[just typed this out in a pm--thought it might of general interest]
While I like twin view very much, it is not that easy to view two different cable chanels. You can only view 1 channel at a time from a cable stb (i.e., you have side by side of the same channel--you can't change the channel of just one image using the stb). The nice thing about this is that if you are viewing a crappy SD feed, the twin images, tho smaller, look great.
But say you want to watch a football game and a baseball game at the same time. You tune in one of them (say the football game) via the stb, but to get the baseball game in the second image you must have a different source (not just input) hooked up. For example, you'll have to tune in the baseball game via an antenna or a second cable input, like directly from wall or (I think but haven't tried) cable from the wall routed through a vcr or tivo. In addition to that limitation, only 1 of the twin images (specifically the left one) can be from one of the the hdmi or component inputs. The right image must come from the anntena, cable in, composite or s-video (or pc???-- haven't tested) inputs.
So, in order to maximize options for that right side image, I am considering a cable card (can you have both a stb and a cable card at the same time?) or 2 cable boxes or testing to see if I can get all the cable channels via routing through my vcr. No OTA choices here, so anntena is out. One big problem though--I noticed after splitting the cable out of the wall last night, that my stb -> tv hdmi connection is now broken (hdcp error). I think the splitter (decreased cable signal??) is the culprit.
While I didn't use PiP much in my newly retired crt xbr, I think I will be much more likely too now with this ginormous screen (and due to some crappy sd). As I mentioned elsewhere, the "screen" size the twin image is 2" on diag. larger (and can even be resized larger) than the retired crt