I have not, and I would not. I have not hear anything especially positive about it, but I have heard plenty that is negative. The world is a big and beautiful place so why waste time and money going somewhere a bit crap? I'd rather stay in a lovely part of the UK than go somewhere shit in Europe.
I stayed on Nesseber (an island linked to mainland with a causeway) which was beautiful and took the boat over to Sunny Beach a few times. I wouldn't personally recommend Sunny Beach unless it's a really good price. If it's the case of a beach holiday or no holiday then I'd possibly go. I would definitely read reviews on trip advisor to check out nationalities staying at the hotel. Although i really don't like hotels with all British people it's nice to have some as entertainment is more likely to be in English. I went end if May early June and it was boiling, the sand was almost too hot to walk on. I'm not sure if that was freaky weather. Another option could be Turkey for a good value beach holiday.
The corruption from the police is awful too. They stop tourists all the time for speeding, or supposed/trumped up traffic violations, and then extract money with menaces from them. I know someone who goes there regularly and he now goes out with wads of cash in smallish denominations for the express purpose of buying off crooked policemen, for the sake of an easy life.