I have a small form factor pc (Gateway SX) with a tiny little power supply (220w) and 2 expansion slots, 1 pci-e, and one that is half the size of the other slot.
I read tons of reviews and needed something both low profile, and that wont run hot, I wanted to be able to play Starcraft 2.
I haven't gotten the game yet but I got the video card and it bumped my windows experience index from 4.3 to 6.7
The video card I got from Newegg for approx $100 (after tax and shipping) and it is a Sapphire Radeon HD5570 PCI-E 2.1 with 1GB DDR3.
I havent tested it under gaming conditions but it fit in the slot perfectly. I use a 32" lcd TV (Toshiba) as my monitor, and I haven't tested any games or dvd.
It seems to me that this is a great choice for performance for people with these limitations (space and power supply). The card has a built in fan so that should help keep things cool.