hmm do you have any stats of how fast it loads and of how fast it can delete the files?
Nope. It deletes things as fast as your hard disk allows for it.
File operations, in general, are very slow compared to in-memory operations ... so, even if you go with separate files for each resource item, you will want to do your load/save in places where there isn't a need-for-speed -- between levels, during a "loading" screen, etc. Having a single file packed with all of your resources won't have much of an noticeable impact if you're doing your file-handling work in that manner.
If you want to see a game that makes use of it, you can download and play the demo for Gem Raider
... see if you have any game-killing delays due to file ops.
... Dicey Curves, Space Mission, Jump Gate, Gem Raider, DareBase, Castle Danger, Keeps & Moats Chess