Personally, I would wait for the Nexus One to get to Verizon and try it out. Or, go to a T-Mobile store and try one out now. I love the Droid, but IMO, the hard keyboard is completely useless and the camera is awful. So for me, the Nexus One would probably be a better choice. Not sure if you're in the same boat.
Aren't they only purchasable online?
Yes they are, hopefully you know someone who has one. Verizon will not be carrying it.
Verizon is carrying it as of March 23rd, according to multiple news articles I've read.