I'd been using WM devices for years, and most recently an i760. I had tried a BB for about a month, and was turned off by what I saw as a clunky and feature-starved OS. That was an older model. Then I needed better e-mail capabilities and something that didn't weigh 100 lbs, so I tried the BB 8830. It took me a couple of weeks to fall in love (and almost every day I thought about ditching it for the WM I was so familiar with), but the i760 finally went bye-bye and I haven't looked back.
Yes, many of the apps are more expensive than in the WM environment, but this is the first device I've found (my opinion only) that handles the role of "PDA" and "PHONE" equally well. My i760 used to get confused when a call came in (a bad sign for a freakin' cell phone), and there were times when it wouldn't answer, even though I was frantically pushing the "send" button and swearing under my breath.
All in all, I've been much happier in the BB environment. It took a bit of time, but it's a relief to be here.