So, I have had the opportunity to test an unlocked iPhone on the T-Mobile network. It is the older 2G service iPhone, but this is perfect for me as most of the t-Mobile coverage in my area is 2G anyhow. Besides, 2G runs with less power and if an application can run on the 2G network, it will definitely run on the 3G without an issue.
So far, so good. Now with a single SIM card, I can develop and test on both Andriod and iPhones without having to have 2 phones and 2 services. Definitely a nice situation to be in.
Here is a good article on Syncing Gmail, Google Contacts, etc.
http://www.google.com/support/mobile/bin/answer.py?hl=en&answer=138740