I've been using the Exchange Server along with a Blackberry and have always wanted an equivalent of Outlook on the Mac.
Today I found it- Outlook 2007 running on Codeweaver's upcoming CrossOver 7.0. I know I could always Parallels or Fusion but that required running the entire windows O/S that would increase CPU utilization which would not only make by MacBook Pro quite hot but also lower the battery life and increase RAM usage.
The previous version of CrossOver only allowed Office 2003 which is also a great subsitute but I hated the fact that fonts were not anti-aliased which made the program look horrible- especially since you're dealing with so much text and part of being a Mac user is appreciating beauty.
The upcoming version supports Office 2007 which has built-in font smoothing making it look quite nice. I am an official beta tester and am liking the new beta very much. Even Word 2007 and Excel 2007 are better than the "2008" Mac versions and launch times are almost the same