Problem is there is no way a 1080p heavily compressed 4gb version of the movie is gonna compare with a Blu ray clocking in at 25+GB and for me that's huge. They will look ok on my 50" Plasma, not so good on my 96" Screen in my Basement HT. but your right I mainly watch big movies on that...
I've checked some of the sizes of the 720p Movies and TV Shows I've bought against their new 1080p counterpart and in alot of cases there isn't a huge size bump, meaning these things are upconverts or very heavily compressed, but I have'nt watched any to see which.