Even if you're looking for a decent HD set, don't discount 720p vs 1080p (there is no such thing as a 1080i "tv" - a display with 1080 lines of resolution is capable of 1080p). Both Chad and Shmokes are right; there isn't a huge diference between 1080i and 720p, but 1080p does bring a bit more detail to the table for some types of programming. And yep, 720p looks better than 1080i on a 720p display, and 1080i programming looks nicer on a 1080p display.
I have an 85" front projection setup that is "only" 720p, and I'm very happy with it. At 50", the visible difference between 1080 and 720 will be negligible for nearly anything you watch. Heck, I have an old(er) 480p ED 42" plasma on which HD broadcasts look nearly as good, if not as good as on my 42" 720p HD plasma.
For $1000 for a flat form factor display, that's a killer deal. My first plasma back in 2002 cost me $3500; my second one cost me just under $2k, and the most recent one (the best one) was $1500. All 42" panasonic panels.