Great questions! It hasn't been tested under severe conditions, but the stub documents that are created are quite small (~500 bytes or so) and I haven't seen significant performance impacts on the databases in which this is in use.
However, that said, I think all of the points you bring up are all things that are being considered for an application update, especially the ability to log to a dedicated tracking database and the ability to capture documents anonymously. Please keep an eye on this space for future updates and if you have additional suggestions, please post them here.
Cheers,
Chris Blatnick