Re: 720p vs 1080i/1080p
Also, remember, there are good 1080p sets out there, and poorly implemented 1080p sets out there. Just because it's 1080p doesn't automatically mean it's going to look good, it's just going to have less of the screen-door effect depending on how close you stand/sit to the TV set. The more important factors, contrast level, color fidelity, sharpness, brightness all contribute to how good the actual picture looks on the TV set, and you have to do your own research and go stare at the different models and select one to buy based on what's most important to you.
Some folks automatically look only at 1080p models because they feel compelled to mate it to their new Blu-ray player, and that's not a bad strategy in terms of warding off possible buyer's remorse for going with a 720p model, just know that you'll most likely be paying a 25%-50% price premium for the 1080p models that look very good, while lesser 1080p models skimp on the video quality to hit that lower price point to lure prospective buyers looking at 1080p models, and those buyers are settling for less video quality for more resolution that may or may not even be appreciable depending on how close/far they sit to the TV set.
Also, unless you exclusively watch HD DVDs or Blu-rays on your TV set, 1080p isn't going to all that useful on HD content provided by Cable or Satellite or OTA reception, since it'll mostly be 1080i or 720p. Most of today's TVs have good enough de-interlacers to produce consistently good video playback of 1080i content. I tend to watch more programming from TV/Cable/OTA on my TV than HDM. Others will have different viewing habits (mainly DVDs and HDM), and that focus will more likely lead them to go for the 1080p models, and that's okay, too.
As a side-effect of getting older (vision-wise), I'm more into "seeing is believing", and try not to let the numbers solely guide a purchase decision. Given the same budget, I won't remove from consideration a 720p model with very good picture quality over a 1080p model with lesser picture quality, or smaller screen size.