What I've mostly noticed with it being slow is anything that might accidentally trigger it trying to ssh to another machine to get an autocomplete list. Since

What I've mostly noticed with it being slow is anything that might accidentally trigger it trying to ssh to another machine to get an autocomplete list. Since it won't maintain that connection it can cause it to happen multiple times while you're trying to tab complete different pieces. I imagine other similar problems with slow file systems or ones with a lot of latency (nfs?) might cause problems. I haven't noticed it elsewhere so maybe there's something I'm just not hitting.