I have a current gen LCD (Sharp Aquos) and am very pleased with the black levels. Of course, its not as good as my direct view HD CRT, but certainly much better than last gen (and hard to notice now). Off axis viewing if fine, too.
However, I believe at a recent expo several manufacturers demoed multi-wavelength backlit LCDs that will be in production by year-end. These are supposed to have superb contrast ratios and solve the black issue entirely. If you’re willing to pay a premium, I’d say wait a few months.
Generally speaking, compared to plasmas, LCDs are:
smaller (although 52" sets are available now)
use less energy than a plasma
are “better” for HD (they are fixed-pixel to a native screen 1080 resoultion, and suffer no screen geometry issues)
don’t burn in
may require bulb replacement (MTF is usally around 10,000 hours…so most people are unlikely to need to)
don’t resolve deep blacks as well
may lose contrast when viewing at oblique angles
are generally poorer at displaying SD content
My understanding is that Sony and a few other manufacturers are beginning to phase out plasma production. Its more expensive than LCD so their margins are lower, and most of the LCD shortcomings can be addressed with newer manufacturing processes, whereas plasma is fairly mature and unlikely to get much better. I’d chose with LCD.