Aaaargh. Please help Viridian select a new TV.

Markphd gives good advice. I will provide a slightly different perspective in 2 areas-
Technology- If you watch sports much (you mentioned movies but did not say if you watch TV also) then the faster response time of the plasma makes a big difference. Add the blacker blacks and you've got a winner, IMO. But I admit to not having seen the latest generation of LCD TVs. After re-reading your post, tho, I see you sit on axis in a room with apparently total light control. If anyone is still making rear projection CRTs, that might be worth looking into.
Resolution- At 720p or 1080i, resolution is quite magnificent. Not sure I would pay the premium for 1080p without any current software. No broadcast 1080p and total chaos at the DVD level. Of course, if money is not an issue, then 1080p WOULD be the way to go. But if I was on any kind of budget I would skip 1080p and use the $ to get it calibrated by an ISF technician. They charge by the input and it can get expensive, but its worth it. I also think that a scaler/switcher might be a better investment than a 1080p set with multiple HDMI inputs but it does require another box and us 'philes know the ins and outs of that debate!

As far as brands go, Panasonic seems right now to be the consensus price:performance leader but a big factor might be what's available at your local BJ's/Sam's Club/Costco/Big box whatever. No one can compete with them- they have driven Tweeter into Chapter 11 and the prices are amazingly low- 60" sets are selling for 1/2 the price of 42"s from 2-3 years ago!!

Finally, for technical advice, you may also want to consider posting on avsforum.com.

If new gen LCD response times are better, then that's great and at that screen size, pixel size may be an issue so that helps the LCD argument. Best to try before you buy, but try to find a place that will let you adjust the PQ, and where you can look at sports, DVD and cable TV (if you plan to use it) Some conventional cable signals look like $ t at 60 or 70" size. Not all sets deal with poor quality inputs as well as others. On some sets, a non-optimal signal is virtually unwatchable, although may be more of a function of source than display. As you probably know, most big box sets are goosed way up on brightness and some other parameters.