I had a BB9700 for two years and the only thing I miss is the battery life, however I use my Lumia 900 much more than my blackberry. The last six months I had the BB I wanted to throw the phone in the toilet I hated it that much, and I probably would have if its trade-in value was lower.
Switching from the qwerty keyboard to the touchscreen of my 900 only took about a day. As far as messaging goes I prefer the style used by the windows phone, I really like how facebook chat and text messages all go one location. App wise, yeah Windows Phone doesn't compete with iOS or android in shear number, but I think it blown out of proportion, because my app needs are more than met.