Hi and to answer your question Mac os X’s marketshare has been rocketing for the whole of 2007, first things you have to know about buying a mac are :

1) If you don’t intend for a All in one solution and look for expandability reliability ease of use and power on a desktop machine , look for a MacPro they can run Vista , OsX , Ubuntu , XP all in one and mostly at screaming speeds 5.9/6.0 on Vista Ultimate 64 bit edition.

2) Ram , dont buy from Apple , they sell them a little expensive.

3) HD Drives, same thing.

4) Video Card , if you intend to do a lot of 3D , gaming video compression the Quadro Nvidia is a great GPU , works great and they have a good bang as a PRO card , if you want something cheaper and yet fast the Radeon X1900XT is the way to go.

5) Screen : ACD 30 inch for pro work , i heard Dell has a cheaper model out but i would not trust its color accuracy.

With this type of machine you combine the best bang for the buck around in terms of computing you can run Windows via BootCamp and winXp will run at native speed, via Parralles , and you wont have to reboot out of mac os X to XP , or run programs via CrossOver . All of these work great.

Adaptation to mac os X is easy if you live in the US since there are Apple store galore , Mac User Groups in your area that are glad to help and teach , if you have been around a Unix system you will quickly find yourself at home quicker than on Linux ,

In terms of support and Question and Answers there is a whole community online at support.apple.com with discussions boards to solve out problems and answer questions. and dont worry they never use RTFM terms there.

Hoping this helps…