I have only been to house of blues for concerts, not to eat here (no vegan options!).
The venue is OK, I think it's decent for concerts, it's small, has a General admission and seating section. Full Bar down stairs and decent bathrooms. The staff has always been decent when I have been there.
The drink prices are about as good as you would expect, especially for vegas. Not sure what else people expect to find. My suggestion is to hit up the bar across from HOB and get a huge freezy drink for $9 with an extra shot. It will save you money (unless you want water).
I would come back here again, and I love Mandalay Bay too!