They do not perform as well as pure EMDs, all else being equal. I've had a lot of success using small modifiers at the beginning or the end I typically use "my" or "the" at the beginning and "101", "247" or "365" at the end. "HQ" is pure genius--I'm going to have to start using that one now.
I haven't seen any difference with putting a modifier at the beginning or end from a SERP perspective. I could see how having it at the end might help a little bit on CTR from the SERPs, but I suspect it would be minor at best.