If you are working on a web app that you can bisect and retest each new version in a few seconds it's an amazing tool.
If you are working on a stack of huge server apps with 1h+ build times, and complicated start up procedures you aren't going to find besect very useful at all.
1h+ build times are probably a result of not doing something about the build times like fixing #include mess, making sure there are no redundant compiles, caching and getting better hardware.
But even if your build times are that ridiculous, git bisect is still useful because it is not just a constant time improvement - having to do log(n) builds isntead of n is going to be helpful no matter how long each build takes.
I've seen projects that take longer to link than a complete from-scratch build of the Linux kernel (and when bisecting, incremental builds do a lot for you on the later steps).
If you are working on a web app that you can bisect and retest each new version in a few seconds it's an amazing tool.
If you are working on a stack of huge server apps with 1h+ build times, and complicated start up procedures you aren't going to find besect very useful at all.