For serious number crunching power, like for instance CSIRO geographical map development ETC, you will not see a mac in the place, bar the secretary, For high end work mac's just don't cut the mustard, at home sure, it will compete but how often do you really put your box through the ringer, 100% cpu load for 10's of hours at a time, granted any Harvey Norman job wont do it either.
Software side ill leave up to others but hardware, I build high end purpose built jobs, and I wouldn't have a hope in hell competing with the big boys if I had to live within the boundarys of planet Mac.
At home PC's I look at it like amateur radio, some go out and buy a top of the line Uniden or such, but the true enthusiast will build his own, and thats something Mac cant offer, there to sort of built to plug in and go. Some see that as good, but I get a sense of achievement knowing I built what im using.
One thing I have noticed is, ACT Mac users SUCK, we had a young lady that didn't have the finance to by a new computer but had been passed on a semi dated Mac, so to point her in the right direction we took her to a Mac users club meeting, a first for us all, spoke to a few people and then she was offered advice on the model she had, she sat down at a table with this guy, and out of his pocket he pulled a clock sat it on the table and said 65 bucks and hour. We just left.....
OZ