I installed Sprint's specially formulated BlackBerry OS 4.5 update on my Curve 8330 last night. The process when smoothly using BlackBerry Manager 4.7 on my Windows Vista Business SP1 PC.
So far things look good and appear to be working well. The one thing that I didn't like was that the pre-installed photos, one of which I liked as my wallpaper, are no longer on my device after applying the update. I haven't had a chance to follow up with other Sprint 8330 users yet to see if they have had similar experiences or not. All in all, it isn't a big deal. I'm sure somone posted the photos on the Inetnet. If I find them, I'll post the link. I'll also try and see if Sprint can confirm the missing photos.
Otherwise, email, the browser, and Documents To Go are all working well. I'll have to spend some more time playing with the new software over the weekend.