I haven't read all the previous posts so forgive me if i repeat any information or if I've missed anything. I really like Mail and iCal, they do everything I need. My g/f and I both use Spanning Sync to keep our iCals the same (via Google Calendars). As far as Office software I've gone for iWork. It can open and save to MSOffice formats and again I've had no problems there. My only wish with iWork is that Numbers could do as many calculations as Excel even though I don't need them and that you could do formulas in Pages like you can in Word. If iWork doesn't suit your needs then look at Open Office. Ver 3 has just been released and I installed it earlier this week. It can do everything that MS Office can so you should be sorted. Anything to stay away from Microsoft.
Thx!