Update - March 5, 2012
I've been checking out some lesser distros, those that are lighter weight and fit for older, lower power computers or fit to run in a VM when you don't have a lot of resources to spare. I tested distros such as:
and several others. What I found was that the quality of most of these distros was lacking, causing difficulty in performing updates, installing new packages, etc. The one exception to this was Lubuntu, which is based on the popular Ubuntu distro, and uses many of the same repositories for software and updates.
Lubuntu is basically Ubuntu, stripped down a bit, using the light-weight LXDE as its default desktop environment. I wen't a step further and also installed Enlightenment E17 as an evern lighter-weight alternative desktop. The result is a solid distro with very low memory requirements and good performance on old hardware.
The truth is, you can install LXDE on just about any popular distro (and E17 on most). If you also disable any unneeded daemons, you can turn any distro into a light weight. The deciding factor for me is the quality of the distro - how much trouble do you run into when installing software and performing updates. Lubuntu comes out on top with no problems encountered.
Update - February 14, 2012
Recently I've stayed with three of the most popular distros, Linux Mint 12, Ubuntu 11.10, and Fedora 16. I got some better hardware to test on, hardware that will run the Gnome-Shell interface, and I must say that I like Gnome-Shell much better than I like Ubuntu's Unity interface.
Also, I've been running Linux inside VMware Player, which allieviates the need for the version of Linux to work well on my wireless hardware. That levels the playing field so that I have no problems running Fedora.
One thing that I noticed, that makes Ubuntu and Mint look very nice, it's the default settings for the font hinting, set to "slight", which makes the fonts look full and solid. On Fedora, the default setting is "medium", which makes the fonts look a little thin and grainy. Having learned how to change this setting, I can now set the hinting to slight on Fedora, and boom, Fedora now has the same good look to its fonts. Playing field even more even.
With those things out of the way, next is the development software. I'm using Geany, Anjuta, Glade3, Gtkbuilder , and Python to develop GUI apps on Linux. I can get all this working on all three distros without much trouble. By the way, I tried OpenSUSE again, and it fell short again here. Couldn't get my dev platform working.
So the choice beetween Ubuntu, Mint, and Fedora largely comes down to looks. And given that you can tweak the themes, you can practically make them look alike. I'm quickly learning to like Fedora above the others. I'm busy reading the Fedora Project documentation, currently reading the SELinux guide, and although I dislike SELinux, I have to admit it is a powerful security tool, and it comes built into Fedora. That's a pretty compelling feature for business and security-savvy home users alike.
My Recommendation for February 12, 2012: Check out Fedora!
Previous Comments from December 10, 2011
For ease of use: Ubuntu. Although I don't like the Unity desktop, Gnome Classic and Xfce desktop work for me. On fast hardware and a wired connection: Fedora. For learning Linux and having ultimate control: Arch Linux.
Linux Mint 12 "Lisa"
Mint Offers the Mint Gnome Shell Extensions (MGSE) to make Gnome 3 more user friendly, and MATE which is a fork of Gnome 2. I found that both of these desktops were broken and buggy, and Gnome Classic mode is the only thing that works right for me. I'm cool with that, but you can run Gnome Classic on just about any distro. Xfce desktop is also a good choice on Mint. I gotta give Mint a fail on MATE and MGSE.
Ubuntu 11.10 "Oneiric Ocelot"
Probably deserves the title of "Best Distro" for ease of use. It's solid as a rock, and looks very nice. I don't love the Unity interface, so I've got a bunch of desktops installed, I'm currently using Xfce.
Fedora 16 "Verne"
If you like Gnome 3, this is a great distro. Run by Red Hat, Fedora is generally very solid. I did run into a problem with my Wireless card going off line after several minutes of working, so I had to ditch Fedora. Not sure if that was just specific to my hardware or not, but I had to ditch.
Very nice looking in Gnome 3, but I ran into several problems. I couldn't make zypper (the package manager) work through a proxy, Gnome 3 wouldn't fall back to classic mode on older hardware, and some dependencies were bugged up when running dev tools like Anjuta. Fail!
Debian 6 and Linux Mint Debian Edition (LMDE)
Older-looking style, but fine performance and stability. Debian is the base of the family tree that includes Ubuntu and Mint. Debian moves more slowly in implementing newer packages to maintain that stability. I give these distros high marks in that regard.
Arch Linux 2011.08.19
This is the distro you want if you want to learn Linux. The install process takes a bit of work, you'll probably have to read the guide, and the guide is very good. Along the way, you learn a lot, and it's so worth it. When you're done, you've got a highly customizable yet solid build, that you know a lot about. This may just become my favorite distro.
Another older-looking distro, it is based on the Red Hat source code. As such, it's solid and it's a great choice as a server in a corporate environment where Red Hat is predominant. You can use CentOS as if it were just a free copy of Red Hat, where as you have to buy a license for Red Hat otherwise you can't use the repos for updates and software installs. Boo Red Hat! Yay CentOS!
While not really Linux (FreeBSD has its own type of kernel), it runs much of the same software as Linux, so it kinda qualifies. Man what a lot of work to install! Getting the GUI setup took hours, partly because the repos were slow. You can also install packages from source code that's installed on the local disk, but man that takes a long time too. I eventually got everything working, and I guess it's all good but it seems like you do get a lot of hangs and failures when getting updates and packages from the repos. Kind of a pain, and for what?
Ah, very cool. This one looks and feels unique. Seems very solid, but the installer is pretty weak, and you need to do a bit of work yourself. I did have some trouble, after the install it wouldn't boot, but on my third try I got it working. Also, it takes some effort to get rid of the LiveCD experience after the install: it continues to logon automatically with the Vector Live account, the install icon is still on the desktop, etc. But after you deal with all that, this is one cool distro!
A variant of Puppy Linux that is intended to run right off the CD and loads into RAM for quick performance. I installed it onto the hard disk anyway and it is tight! Super low memory requirements. Kinda fugly, but it's a neat little distro with potential for situaltions where you want something really small and fast.
I also tested PCLinuxOS (feh), Mandriva (yawn), Chakra (needs work), Gentoo (kinda cool, especially with the hot girl wallpapers installed by default, didn't see that coming).
In the grand scheme of things, I realized that Linux is, generally speaking, Linux. What you should be looking for is a a distro that is well integrated, that is, the provider has done a good job testing all of the packages and dependencies so that everything works together without a lot of bugs and missing dependencies.
We'll keep you posted as new versions come out...