It works for almost everything I try to find. It might take a few tries, but I can usually find the mail I was looking for.

Usually when I change jobs I have had another non Gmail account but I have never found the search as good. I have an outlook web client at work and that doesn't find things. Maybe its me being dumb and remembering different phrases from what is actually stored, but I almost always manage to finds what i am looking for in Gmail. I can't say the same with other clients.

Its just a pity that I have to give up my privacy to Google for it.

Well, it can't even find all instances of a single exact ID.

It's what you'd expect of a cloud service though, they really don't want to go through all of that data.

Any native client though will just go at it and return proper results.