I know what you mean. I also have the best buy version, so I just followed This guide and all worked well. Then, in order to get Lion working (even to boot into the installer partition) I simply installed the newest version of Chameleon (the one that comes in the package is not up to date enough apparently). Everything is working except the trackpad, 6250 agn, battery indicator, and hdmi (well it works when using hdmi to dvi adaptor as long as you have it plugged in before you boot up).
The video card is reported at ATI 5000, but I think it is just aesthetic, as all is working ok so far. I DO have some crashes if I tax the system with lots of open windows, and maybe some video, and some music (maybe a heat issue, because I would have that problem sometimes in windows too with turbo enabled).
Lets improve some more?