Start off with calibrating your display (If you have a sony title like Taladega Nights, use the easter egg [menu]7669). Alternately, if you don't have a Sony disk at hand, (if) your display has a "movie mode", select that first. Most default settings are too high.
I would defintely start with an animation title just to see the limits of clarity that you can get on your system. Even if you're not an animation guy, Ice Age II should be there for comparison. (And in case you have an urge to demo your setup).
For your own viewing, Black Hawk Down shows a lot of detail, along with giving your audio gear a good workout. A lot of Saving Private Ryan style gore, so this is not for children.
Kingdom of Heaven is my favourite so far in terms of a whole movie. Being a Ridley Scott fan since BladeRunner, I was disappointed in the theatre. That version left a lot of gaps, this cut was more watchable. Even though the transfer is accurate throughout, be aware that the start of the movie shows the ugly side of medieval France, meaning all the poverty and bleak landscape doesn't look good. It was only after they reach Messina, that the money shots start to pile up. Main knock against the movie perhaps is that Orlando Bloom looked out of place in that role. (I personally thought that "didn't want to be there but have to finish the job" accurately portrays Scott's intent for this character)
Some thing to watch out for is that the highdef transfers often highlights what the director put into the movie as well as any imperfections in the final edit. The number one complaint seems to be that there is too much grain. In some cases, the grain is in the film and also the digital master. In others, they appear to be compression artifacts as the bitrates are set too low to fit in the disk. Another complaint is that colors may look flat - meaning they look gray or brown like the real world around us really looks --- instead of shiny or vivid like you want movies to be --- so choose your demo movies well.
I like natural grain, but others (especially non hardcore movie fans) may not tolerate it.