On the XBR4 vs the Samsung LNT52F comment, they use the same LCD panel fabrication but each company makes a different processing engine.
There is a pretty unbiased review by Robert Heron of Ziff Davis. He actually measures the picture accuracy, color saturation etc with actual equipment. If people have actually seen a Vizio TV side by side, they'd realize sometimes it is not worth the extra $200-$500 for a similar performing TV (with extraneous features) if they are on a tight budget. I will admit that picture quality on the Vizio is not on the same level as the Samsung tier, but Vizio and the consumers know that going in.
According to Heron, Vizio is quite acceptable for budget line, and Samsung is next up for mid range (Sony if you don't want glossy). The best HDTV is still a Pioneer Kuro plasma, and for those who think plasmas still burn-in after 10 seconds, they no longer do. They just use much more power than LCDs. For Film, TV (sports) and gaming, the plasmas are still the best money can buy.
Vizio is a Californian product and is not prepared solely for any specific retailer (but is targeted for the American Market). You can find Vizio at many retailers. If it were not for Vizio, every other TV, Samsung and Sony, would be priced probably 20% more, so b*tch all you want, and buy what TV you want, but you owe some of its reduced price to Vizio.
So for people on a budget, instead of buying an off brand Walmart HDTV like Westinghouse or whatever, Vizio is a better TV.