Damian, welcome to the forum. There are many threads on here discussing Treo vs. BB and Pocket PC vs. BB. I've used all of these devices and wouldn't trade my BB for anything else now. As a matter of fact, when I owned a Treo and numerous PPC's, I used to always check out what was coming out to see if there was something better.
The number one benefit for me is push email. I think my 8700 is incredibly stable and reliable. The PIM interface syncs well with Outlook too. Yes, I give up some of the multimedia functionality next to Treo's and PPC's but, honestly, never really used them that much anyway.
I've found very good programs that compliment my BB so I don't think I've lost anything at all by switching. If you're a die-hard PPC guy (like I used to be), give the BB a try for awhile. You might be quite surprised!