I'd like to address this BS that many people seem to be throwing around. PRO's are not people that F-around with their systems. Unless you are a professional system technician you DON'T perform surgery on your computer. Professionals in the fields of film, graphic design, audio production, jims home business all buy computers to do a job they don't by a computer to "tinker" with. That's for 16 year olds who don't actually have a "profession". Professionals write off their computers as a business expense. If it costs them $750 extra that's part of the cost of doing business.
I'm frankly tired of people who think that people trying to do a job actually want to dabble with the inner workings of a computer. This is part of the reason people buy a Mac in the first place. Heck I've worked in IT for 8 years and I'm sick of upgrading and troubleshooting. It bores me to death. Some people would rather get things finished, be done with it, and move on. I'd rather be outside in the sun then upgrading my harddrive to increase performance.