This is Very cool. I've got a little one that soon enough will learn how to use the TV and remote and I'd like to have some Parental Controls on PMS. I too would like to see a folder level block that wouldn't require me to add file after file to the .ini file. Since I'm on a linux box I've been creating directories for a "theme/rating" and then creating symlinks in that to the files in my "All" directory. Being able to put a lock on everything other than the "Kids" dir would be nice. I also couldn't tell from the docs/demo if you can have different unlock codes for each rating level. That way you can leave the G rated movies unlocked for the little kids, and give your 10 year old the key for the PG rated stuff and your 14 year old for the PG-13 and below while retaining the key for the R rated stuff and above for yourself.
Another tweak to this would be to auto lock everything again after a certain (configurable) length of time has passed since the server stopped streaming. That way if you're up late watching an R rated movie and forget to re-lock everything, your kids can't get into it all when they get up in the morning.