I'll follow up later with a Moe indepth response later, I'm on my phone currently.
1) decide what size you want, and how far you sit from the TV. Many times the size to distance ratio is such that the difference between the two resolutions is imperceptible.
2) you can go large (50") for 1000-1500 in 720p plasma. 1080p will generally run 2500+.
3) are you going to be investing in bluray right now? 300-400 for player, 20-30 per disc. Add that to the 700-1000 extra for the 1080p, and you've more than doubled your costs.
my personal opinion when I upgraded a month ago, you're going from old school to widescreen high-def TV. That by itself is a glorious upgrade. How much more bang for the buck will you really get out of 1080p?
If I spend a grand now, its easier for me to justify a second TV in 5 years or so, perhaps for the office or bedroom. If I spent 2500 on 1080p, I feel like I've already spent the 2nd TV money.