I had the Droid X from it's release until around December of last year. I absolutely loved the large screen on the phone, and I was fine with the on-screen keyboard (Swype definitely helps things). But I kept finding myself drawn back to wanting a physical keyboard. I had the original Droid for awhile, so I looked into the Droid 2 Global a bit. But I really liked the form factor of the Droid Pro's keyboard. The only problem was that I didn't think I could live with the small screen size after having the X.
Curiosity eventually got the best of me, and I decided to give the Pro a spin. I'm extremely glad that I did. I love this phone more than pretty much any phone I've ever owned. The screen size, even coming from the Droid X, really isn't a problem at all. Everything is still very readable, and it's nice not to have an on-screen keyboard taking up half or more of the screen so that you can actually see more of what you're typing. I normally start to get bored with a phone after a couple of months, but I have yet to tire of the Droid Pro, and I don't see it happening anytime soon. The usefulness of the form factor for me far outweighs anything I might slightly miss from something like the X.