I had the same question myself. I was looking at $300 27" TVs and a $120 27" Apex kept calling me over (Circuit City with 10% off any TV coupon), luring me with the low price. So I looked a bit more closely at them. The in-store display had multiple defects, due to what looked like crappy design (such as the front button panel nearly falling off). But that wasn't enough to sway me.
I looked at reviews, and the Apex TVs always were rated right at the bottom for picture and sound quality. That almost did it, but not quite.
What finally swayed me away was the absolute lack of anyone with happy stories about them. Sure one person's opinion could be a fluke, but the stories of good service are absolutely non existant. Combine with all the above, and I decided I'd rather pay $300 for a TV that should last 15 years than a $120 TV that may last 3.