Dimly lit room: Plasma, LCD, or DLP

As stated above all 3 work great in a dim environment. 120hz is only a factor if you watch a lot of live sports..other than that the difference will not be noticeable if you buy a Tier 1 LCD (Sony,Sharp,Mits,Samsung). The video processors are good enough in these 60Hz models..I doubt you'd see a difference for the extra cost of 120Hz.

Blacks will be better on a Plasma as a whole, but there are some trade offs that plasma lovers do not mention.

Though the blacks are a little deeper on my plasma, my LCD has better shadow detail. In other words, on dark scenes I see more detail on objects like buildings and the side of a person's face that is away from direct light.

This is also important and easily visible when you do a side by side comparison on the same material. As time goes on a plasma will grow dimmer(it will start to lose its brilliance).. an LCD doesn't.

A plasma is more susceptible to burn in... LCDs are not.

So you really have to look and decide what is most important to you and where to make a compromise.

Neither is perfect..both plasma and LCD have wider viewing angles than DLP. LCDs look best when viewed directly or from a tighter viewing angle than a plasma, similar to a DLP. Though not quite as critical as a DLP.

Pick your poison.

Plasma TVs are very energy inefficient. LCD TV are much greener.

A 42" class plasma will consume about the same amount of electricity for 3 to 4 hours of daily use as a modern full size refrigerator consumes in 24 hours. The WSJ says to add $200/year to your electric bill for the purchase of each large plasma (this obviously varies by location and usage). LCDs are more efficient, but still relatively high energy users. Roughly a third less than a plasma. Old-school CRTs are by far the more energy efficient.

LCD/Plasma power usage:
http://reviews.cnet.com/4520-6475_7-6400401-3.html

Plasma are best overall. As Chad says above - LCD's do not do blacks well at all. IMHO there is NO comparison (I own both)