There was content available from all of the BBC channels... I personally don't have digital reception at the moment, but I was able to watch BBC3 programmes like Titty Bang Bang because of iMP (and very good it was). In fact, there were times when content became available to download BEFORE it was broadcast. There were also listings for programmes that were being repeated through regular broadcast - result for me as I got to see a documentary I would not have seen otherwise.
Hope this helps...
Matt.