I crrently have the XFX 6600GT, and I can say it works great for me. I've e-mailed their tech support a couple times about nVidia driver bugs and they've been quick & responsive. I've in the past e-mailed MSI and they for the most part refuse to provide tech support. For a while, MSI would not even allow you to e-mail them, all product support had to be through the retailler. They've probably changed their stance a bit since then - though if you go onto an MSI support forum you'll hear about all the masses of people who absoluely hate MSI's tech support (and I've seen them, I don't think MSI hosts that support forum anymore though, no one from MSI ever monitored the forum anyways even though it was hosted by them).
So what am I saying? I'm saying that for any given company you will find groups of people who absolutely love them, and groups of people who absolutely hate them. Don't take the advice of a single person or even a single forum. Like, I own a Dodge Dakota, and there's a forum site for them, and in the problems forum everyone thinks they're the worst POS's ever made and every single person experiences massive problems. But over in the custom audio forum, most everyone loves their Dakotas and wouldn't hesitate to buy another one. Get the point?