IMO a major obstackle for developers to get the most out this additional feature (for example make use and rely on harddrive caching). The 20GB mostly seems useful for demos and smaller downloadable games, for high definition movies even just one Blu-Ray movie in full quality will likely not fit on the harddrive (and Microsoft needs a serious server upgrade if they are serious about the high definition movies distributed over the internet stand-point!).
Currently I mostly store ordinary resolution music videos, MP3 and photos on my PS3, 60GB is quite a lot but I am happy it's easily possible to upgrade to a bigger harddrive from any company myself. I did buy Lemmings, Blast Factor, Super Ruba Dub and Fl0w as well! Next up will most likely be Warhawk, the first game which will really require some space!
