If you have to have a keyboard, then either get a Motorola Droid (also called the Milestone outside of the US), or wait to see if the Samsung Galaxy S Pro or Epic or whatever it'll be called ever comes out. To be honest the Droid/Milestone is a little old now.
If you like rooting and the latest and greatest ROMs, go with the Nexus One.
If you want the current best phone on the market, it's the Samsung Galaxy S.
I still have my G1, and can't upgrade for another couple of weeks. I've tried just about every Android phone out there over the past few months, and the super screen on the Samsung Galaxy S (which is the best in its class), combined with the fastest touch screen in the world, and super-fast graphics processor just means it flies along.
I tried typing really fast on the Samsung Galaxy S touch keyboard, and I can honestly type just as fast. With a bit of practice I think I could type faster than a physical keyboard because it corrects my typos very well and you don't have to push the keys until it clicks, which takes extra time. Also it has Swype, which is the virtual keyboard that was used to break the world record for fastest typing of a text message on a mobile phone. See the video here: http://www.youtube.com/watch?v=33Mt2z-GoJk