A lot of PC gamers have switched, imo, just because of the costs of constantly upgrading to the cutting edge is ever higher and let's face it, 10 years ago, a bump in power sped everything up, now most computers, even laptops, already have 64 dual cores. Aside from games what uses that kind of power now? Vertually nothing. But gamers still spend hundreds to thousands more just to play the lastest games, or... buy a 360 or PS3. Let's face it, even the lowest end computer will run all your utilities, web browsing, etc. So you can get both a reg laptop and PS3 for less than a gaming rig (which needs constant upgrading to play the lastest games to the fullest).
360 makes more sense to me as it has more PC style games, but a lot of my PC gamer friends hate Microsoft with a passion and will (eventually) buy a PS3 instead (to go with their Wiis).
There was talk of Sony coming out with Linux and a keyboard for the PS3, and that'd get some of that crowd to buy in as well.
