I have not been 100% successful at getting rid of my Microsoft PIM. I am still using Entourage for Calendar and Tasks. Thankfully I am not using outlook for anything anymore. The apple PIM (address, iCal, etc) do not sync categories with my Treo, and all other (non MSFT) alternatives have one draw back or another. So instead of buying another package that will work but still be lacking in one or two key areas I decided to stick with Entourage (i already bought it) and live with its drawbacks for now. I sync address book contacts from entourage and address book via a sync conduit. That lets me keep my Treo updated, and have Mail, Bluephone Elite, and iCal have the latest contact information also.
So far this setup has been working out for the most part. I am also doing 99% of my day to day “office” work on my Mac now. I still use my Thinpad and desktop computers for specific tasks, but my Powerbook is now truly my main computer, and I wouldn’t have it any other way (right now).