Most of your questions have been well answered but here are a few more factors to consider.
* How does one decide between the X, 2 and Pro?
Use pdadb.net to set up a custom comparison chart. Here's yours:
PDAcomparer | PDAdb.net - Comprehensive Database of Smartphone, PDA, PDA Phone, PNA, netbook & Mobile Device Specifications
Over the 2-year contract for this phone you will spend about $2,000. Life's short. Get the one you want.
First the Droid 2 is being replaced by the faster and thinner Droid 2 Global. With a 3.7" screen, Droid 2 Global is exactly the same closed dimensions as the Droid Pro with a tiny 3.1" screen. The Pro at 320x480 is a third the resolution of the other phones and the lowest resolution camera.
As you mention the even bigger screen and better camera is the Droid X. And the over-all volume in your pocket of the Droid X is less than the Droid 2 or Droid Pro.
If you want the smallest volume in your pocket, get the Droid X.
Droid 2 Global: 61 x 119 x 11.7 millimeters = 84930 = 5.18 cubic inches
Droid Pro: 61 x 119 x 11.7 millimeters = 84930 = 5.18 cubic inches
Droid X: 65.5 x 127.5 x 9.9 millimeters = 82677 = 5.04 cubic inches
* Is there a spell check for the X or 2 now or in the future?
See the
Getting Started with Android - Tips and Tricks section on
Keyboards. Spell check is built in to the keyboard apps. It checks as you type.
* Does it make sense to wait for the new 2.3..?
If you are going to wait for Gingerbread, why not wait a little longer for Honeycomb? But if you will wait a little longer, you could get Ice Cream! And if you wait a little longer, "J" might be Jam!
The point is that Google and the manufactures will always have the next latest and greatest features coming just around the corner. Get what meets your needs today. In a year or two you will be upgrading again anyway and all your apps and contacts will carry over to the next phone.
* How hard is it to get use to the screen keyboard?
It's now the other way around. How hard is it to use a physical keyboard? Again, take a look at the
Keyboards section. Physical keyboards are slow. It is
Swype that has set three
world texting speed records.
I am actually much faster on
Swiftkey but because it predicts words for you, it's deemed to be cheating and is not allowed to set Guinness Records. Better still use it's voice to text features. Also for amazing voice commands, consider
Vlingo.
May I ask why you are not also considering other phones like the Samsung Fascinate or Continuum or the HTC Incredible?
In the end, get what feels right to you. It's like buying shoes. No one else can tell you what will feel right to you. Go to the Verizon store and try them all. Get the one you like best. If within 30 days, you don't like it, return it and get something else.