I have a 42" plasma that i got two years ago... i love it and have had zero problems but it is out dated and twice as heavy as plasmas these days.
A couple of things to remember is you can get into a plasma for cheap these days via Sams, Costco, Walmart, or I even have an HEB selling a 42" for $900...
LCD is lighter and better for mounting although both are acceptable. Plasma looks better from further away while LCD is much better than Plasma in close quarters and I believe Plasmas have better viewing from angles than LCD...
LCD you do not have to worry about burn in and they should last a little longer...
DLP, I do not know much about... is that available on flat screens or bigger bulkier units only?