PDA/Smartphone for Windows and Mac

I'm not sure where this topic belongs or if it belongs here, but here goes.

I'll be giving up my Treo 700p smartphone soon. I need a smartphone/PDA that works well on both Windows and Mac platforms. I can't stand the Palm software for the Mac. I've been a Palm user since its inception and am clueless about what else may be appropriate for my needs. Any suggestions? And a suggestion for converting my Palm PIM contacts and events to whatever platform I go to? Thanks.

What exactly do you need out of a smartphone? Knowing what your requirements are will help narrow things down.

All I need is a phone and PDA (for contacts and events) in one. While I don't really care about internet access at this point, it might be something I would use down the road. That's it. Thanks.