You all were talking about HDTVs and I think you may be a little misguided.  Or maybe I am…  120hz TVs are actually a great thing for movies.

So, video, traditionally, is filmed and played back at 30 frames per second (actually, color video is at 29.97 fps) [side note: the first video which was in black and white (b/w) was broadcast at 30 fps exactly and when they introduced color they had to slow down video (to 29.97 fps) to make it fit within the same bandwidth to ensure people with b/w TVs could watch color broadcasts and we’ve kept 29.97 ever since]  Also to note, video that we are used to, i.e. video before HD mostly, is interlaced.  Interlacing is a trick that TV set producers and broadcasters came up with that helped compress the image down so it can be broadcast more easily.  With interlacing, each frame is broken up into fields which are called odd and even fields.  However, because of persistence of memory, the deficiency in all our minds that make video and animation work for humans, it’s so fast that we don’t notice that the TV is showing half a frame at time, it’s that fast! I know its a little weird but basically SD video is called 30 / 29.97 which refers to the frame rate but it is also understood to be equivalent to 60 / 59.94 if interlaced.
And film, traditionally, is filmed and played back at 24 frames per second, exactly.  Much like how letterboxing and 16×9 TVs have been introduced so people can see movies as they were intended, we can now get movies at home in their native frame rate.  There are many HD video formats like 720p, 1080i and 1080p.  720p and 1080i have frame rates of 59.94 which is double 29.97 so its a simple conversion for whatever you have to interpret the video (your bluray player, your dvd player, your cable box…) to make the video workable on your display.  The trick here to remember for these formats is that 1080i is usually called 1080i60 or 1080i59.94 which refers to the fields as mentioned earlier and is really 30 / 29.97 fps whereas 720p is usually called 720p60 or 720p59.94 is actually 60 / 59.94 frames per second because its progressive (Interlaced breaks frames into two fields and progressive shows full frames at a time)  1080p has two main flavors; 30 (or 29.97, I’m going to stop showing both, I think you get the idea) and 24 (Ok, I lied, this is actually 23.976 which was done to make it easier to convert to the 30 / 60 formats easier)  We can watch 1080p video in 24 frames per second now!  We can watch movies in 1080p in the frame rate it was intended!
So, after all that here’s my point…  If you have an HDTV that can play 60hz, your tv has no problem playing 720p60 or 1080i60 or even 1080p30.  The math works perfectly for the TV.  For 720p and 1080i, the TV needs to do nothing to display.  For 1080p30, the TV just has to slow down by half.  Easy math, right.  Now for 1080p24 the math is not as easy so it doesn’t work out to well.  If the source is 1080p24, your HD video player usually just changes the video to 1080p30 to make easier… either way its bad because its not the best way to convert.  If you have a HDTV that can play 120hz, all the 30 and 60 frame rate formats will play normally.  The TV just has to reduce its own frame rate by 2 or 4.  For 24 frame rates, it has to reduce its frame rate by 5.  Every format is happy with 120hz!  Now 240hz is unecessary, as far as I know, its a marketing trick.  Oooh, 240hz is two times better than 120hz.  Avatar looks very strange on HDTVs because its so damn clear.  Film just isn’t as clear as video has become.  You can get your HDTV to “smooth” out any of your video to take “advantage” of the higher refresh rate of your tv.  It’s like how you can stretch a 4×3 (SD video) to your 16×9 widescreen TV and it’ll look like shit.  HDTVs can do all sorts of stuff to make your video look dumb.  You just need to look at the setting and see what you like.  If the video is too smooth, look for a setting… Although with some movies, like Avatar you may just be SOL.
That’s a lot of stuff, and I apologize.  Here’s the condensed.  120hz TVs are actually good because they can show video that is 24fps because it is a multiple that can work with 120hz but 60hz cannot make that claim.
My source for all this, I work in Post Production and spent some time as a Tape Operator… sexy huh?
I tried to keep it simple but I think I failed!
Thanks guys,