I've had my 42 Inch Vizio 1080p LCD for 2years now it's running smoothly.. perfect hdtv for the price if your trying to save some $ it comes with a 1yr warranty as well.
As far as 120hz .. read this article
http://ezinearticles.com/?LCD-Flat-S...ney?&id=963392
playing Blueray in 120hz definitely looks better...
Look at this press release from Vizio though:
They are launching 240hz LCD's this Summer with very high contrast ratio's
http://www.vizio.com/about.aspx?cid=2888&id=1318