I have had my 8900 for a few weeks now and love it.
I used an 8320 before and an 8100 before that.
In comparison to the 8320, the 8900 looks and feels more "Professional". I loved my 8320. It fit well in my hand and I could find accesories anywhere.
The 8900 fits well, too, and seems lighter and "firmer" than my 8320. The screen is MUCH better than any other phone I have ever seen. The keys are firm, easy to find while not looking and feel good.
I don't like the MicroUSB port and I don't like where it is located. But, I guess that is going to be the standard (in 2012) and I had better get used to it. I would also like to find more accessories for the 8900. (Like a silicone case with a detachable swivel clip...ARE YOU LISTENING BODY GLOVE?)