As with performance it really depends on your workload. For mostly reads the performance should be quite good since access is mostly passtrough. This is almost true with writes.
Reading on "history" has a small performance penalty since if you are reading files which are packed they need to be unpacked on the fly.
Listing the "history" is quite fast. We tested on the WordPress repository that has around 17k commits and it takes ~4s first time and less than 1s afterwards.
