My young companion and I recently spent a week here and, all things considered, we had a great holiday. The staff were friendly and helpful, which in the last week of the season was impressive. The food was nutritious and plentiful, the waterfront was well-manned and ran a range of activities, there was lots of other games available on land, and people who only wanted to read their Kindle on a sun-lounger could do just that.
On the downside, the hotel resembled a 1970's Black Sea resort for middle-ranking KGB agents and their families. The beach was not sheltered and there were usually sizeable waves which made it trickier for beginners to get up on windsurfers, and the weather, as you'd expect from the location, was not consistently sunny. Then again, the flight was short and, if you are canny and get a decent discount on the holiday price, it's good value for money. Oh, the booze is sold at London pub prices (I suspect at quite a mark-up on local prices), so be prepared to fork out easily £100+ for your bar bill for the week, depending on thirst.
Overall, as long as you get a good price, you will have a good time at St Lu.