These look like very good deals on very good HDTVs. My reference is the RTINGS website, URL: http://www.rtings.com/tv, where Samsung and Vizio units are extensively reviewed (sorry Hisense). I pay attention to viewing angle and actual refresh rates. Your priorities will likely differ from mine.
Woot’s warranty is 90 days, which should be plenty of time to determine whether you have a problem with your set, like broken or defective connections, burned out pixels, etc. Woot has always been very fair with me when I’ve had problems with my Woot purchases.
Of note, many of these sets are discontinued models, but have been replaced with models that are not necessarily better, depending on your requirements.