we've recently bought a panasonic viera (the 42" one). Bit of a downscale from the 50" samsung DLP projection we had before, but the picture is better-its not as pretty as the samsung though (that was my dream TV that i'd been eying up for 2 years, but had to go back because me and rich were suffering from 'The Rainbow Effect').
if you're going for a large screen, i would say that plasmas are better than LCD. I've found that with the large LCD's (had one and sent it back before the samsung), you lose the contrast, and anything dark just becomes black-you struggle to make out outlines, to see parts of a face etc. The Vieras pic is fantastic, but the sound's a bit naff. We run our sound through an amp, sub and speakers, so we don't have to listen to it. Its actually probably quite good, but we've not listened to a TV through its own sounds for years. DLP projection tv's are good (we had a standard rear projection, which are ok, but you have to sit right in front of the screen, and they're bulky), but because of the 'cinema technology', some people are sensitive to The Rainbow Effect (the image is projected from the back rather than on to the screen, which is why you don't suffer it at the cinema. Apparently.), and it can make watching TV a chore-when you look at one part of the screen, then look at another, you see rainbow trails across the screen.
LG have a
gorgeous 50" LG plasma (which we would have got over the one we have now, but couldn't justify the extra £600-until comet reduced it by £300 only a week after buying out viera!!!!!). The picture is really good, and it looks pretty too (its all about looks for me!!!).
as for Sky HD, we ordered ours in the middle of April, and got the installation day of 10th June. A few weeks ago, we received an apology letter moving the date to the 23rd June. Depending on where you live, i doubt you'd get an installation date during the world cup.
another thing you might want to consider is if you're going to buy an HD ready DVD player. If you are, you'll need to either swap between the sky and dvd HDMI cables when you're watching one or the other, or get a TV with two HDMI inputs (the viera has 2, most have 1).You can get HDMI splitter switches which allows you to connect two HDMI leads to the the TV, but they cost a fair whack-about £100 i think.
good luck in finding one!