It's absolutely very limited. It has a shortcut for ∞ (Option+5), but "Greek letters" is too large of a set for the space provided.
But being able to do that let me do data entry on documents written in Swedish (which has the additional characters of é, å, ä, ö, and à) after about 10 seconds of ramping up figuring out where the desired keys were.
I'm sure there's a summary somewhere on the interwebz.
