I am a very avid Mac user and a big enthusiast as well. I use a PowerBook G4 for managing a computer network and all things related (writing documents in Word, creating spreadsheets in excel, etc.) It is a great computer and easy to use.
Microsoft Office is available and provides the following progams for Mac: Word, Excel, Powerpoint, Entourage (Outlook), and Virtual PC (run Windows programs). Entourage is Personal information manager on Mac instead of Outlook - it does mail, calendar, etc. Pretty much everything Outlook does but with a slightly different layout.
Photoshop exists on Mac also - check out
www.adobe.com for more info.
As for limitations, it's a "the glass is half-full or half-empty" kind of thing. There are far fewer games available for macintosh than for PC and the business programs are limited but there isn't anything you can do on a PC that you can't do on a Mac although you may do it a little different on a Mac than on the PC.
I find using a Mac is an absolute joy and overall easier to manage and install. There is a great article in the December issue of Maximum PC (I think) that one of the editors wrote about his experience in switching to a Mac. I'll see if I can get the specifics.
I don't use a windows machine anymore unless I have to (my company has some custom software that runs on windows and not mac.) Even then, I could run it in Virtual PC but to be fair, it's a little slow.
I hope this helps.
Carvel