This appears to be a 50" 1080p display, so I don't understand this talk of 720p. [edit: now I do; it really doesn't accept 1080p sources, although the display itself is 1080p resolution. At the time this TV was made, there were no readily-available 1080p sources for consumers.]
How far away from the TV are you when making this evaluation? HD looks better the closer you get (within limits, obviously); the optimal viewing distance for 1080p on a 50" display is around 6 feet. See this chart:http://s3.carltonbale.com/resolution_chart.html
With any TV, and especially a rear projector, miscalibration can often mask the benefits of HD. If you haven't calibrated your display, doing so is strongly recommended. For starters, this thread
may offer you some examples of optimized settings you can try.