I run a Macbook PRO with Entourage and a PC with Outlook both tied to a hosted exchange server (Mailstreet). Seeems to be the best solution for me.
If you are comoing from using Outlook on a PC Entourage takes some getting used to. I do not like it near as wekk as OL (can't believe I just said that).
Supposedly MAC OS 10.6 (snow lepord, i think) will offer exchange support for native mail, ical and contacts. SO... goodbye Entourage..
I have been playing around with an ipod touch (Via WiFi) with activesync set up on top of BES through Mailstreet. This is currenlty the closest thing I know of to what I think 10.6 will offer. The one thing I REALLY LIKE about this set up is the ability to look at and sync BOTH of my calendars wirelessly via exchange/activesync which i cannot do via BES. Almost made me want to buy an ipohne for my weekend phone