Step 1 - On your Android phone, launch the Market app, and search for vCardIO. vCardIO is a free app that lets you export your contacts to a vcf (vCard file). Install vCardIO onto your Android phone.
Step 2 - Launch vCardIO, select "Export All Groups", then click the Export button at the top left. The vcf file will be saved to the SD card.
Step 3 - Connect your Android to your PC with a USB cable. To make your Android appear as a USB drive to your PC, you may need to set the phone to allow a data connection. There's apparently different ways to do this depending on what phone you have. For me (I have a crappy Motorola Backflip), I had to go into Settings - Applications - Development and enable USB Debugging, go figure.
Step 4 - Once your Android shows up like a USB drive on your PC, open it and find the vcf file (by default the file will be called backup.vcf).
Step 5 - Attach the vcf file to an email to yourself that you can open on the iPhone.
Step 6 - On the iPhone, open the email containing the attachment using the Mail app. At the bottom of the message, find the attachment and click on it. Your contacts will be displayed.
Step 7 - Click "Add all Contacts"
That's it! Hope that helped. I'll reserve judgement on my opinion of iPhone vs Android. I love the new iPhone, and my Android was a cheap one, old, small screen, too slow, bad carrier, so it's hard for me to make a fair comparison. I'm sure I'd like a hot new Android too. Gotta say though, I'm diggin' the iPhone so far.