The infiltrate helpfile states you can infiltrate from hiding, but I've stepped out of the shadows 100% of the time I've used it on doors.

The skill improvement rate also seems to be abysmally low, with two improvements to infiltrate and zero to advanced lockpick after a few hundred uses of the skill on a variety of locks. Is advanced picklock even being checked? I can Pick Lock all sorts of things that I can't Infiltrate, despite the two skills being at similar %s.

Also, is it by design that the skill only takes mana when used on containers and not doors? I'm not complaining, as the skill would be virtually impossible to perfect with how high the cost and how low the training rates are.