RIM has provided some good guides on how to setup BIS 2.5 and what you can do with it. Remzi has done me a favor and emailed a few my way. Let me know if I missed any.
What is required to get BIS 2.5 to work – Essentially tells you that you need OS 4.5+ and tells you how to resend your service books.
New features you get with BIS 2.5
Configure HTML email messaging support in BlackBerry Internet Service 2.5
Supported native file format attachments in BlackBerry Internet Service 2.5
Supported media types on the BlackBerry smartphone
Good reading if you want to familiarize yourself with all the features. Let me know if I missed any.

SX86 Not Registered
Posted: June 30, 2008 at 6:47 AM EST
Does any of you are able to have HTML Email with Telus ?
I’m using a BB 8830 with OS 4.5…
ggmarcus ( View Profile) Newcomer - Posts: 3
Posted: July 27, 2008 at 8:03 PM EST
I amusing sprint and have the 8330 curve with os 4.5.0.51 and some of my othere coworkers have it to and some can download and save attatchments and some can not. Does Empower make it so you can no tdownload them? I have empower and the others do not?