I switched from Blackberry to the Verizon Droid X at the end of the summer. I have been waiting for the iphone to come to Verizon for a long time, but like BalletPSM, I got sick of waiting.
The droid marketplace has a large number of apps that are available, both for free and for small fees. Some are useful for SM, others are just plain fun to have. (I have fallen in love with "Useless Facts" just for the fun worthless info that it provides
) At any rate, I already have gmail and so it was easy to make all of my email and such work well together. The app Marketplace grows everyday and so I suspect that within a few years, it will probably come very close to rivaling the iphone app store.
All of that being said, ultimately, it comes down to what you like. While there are a lot of similarities between the Android phones and the iphone, there are also a lot of differences so you just need to play with both and figure out what you like. There other thing to keep in mind is that there is only 1 iphone (okay... 4... the original, the 3g, the 3gs and now the 4 - but they are all basically the same software, just with more advanced features, and all made/distributed by Apple) however, Android is just an operating system and there are A LOT of different manufacturers making phones that use that operating systems and some of them work much better than others.
My suggestion is do your research and then try it out!
Good luck!