After spending 3 mothns in the Black Sea area of Romania, this is my feedback:
Romania in general is not expensive, but in the Summer the prices in Constanta and Mamaia (the Black Sea areas) almost double. So we ended up spending way more that expected.
Power cuts: I stayed in Mamaia, and in July-August almost every week there was a power blackout in the area.
The food is not too diverse, is pretty much average Easter European food everywhere. Sushi is not really good, Thai and Indian food is impossible to find. The only highlight for me was the Greek restaurants.
The Sea in Mamaia is not that nice, most of beach is FULL with sunbeds, loud music, and is almost impossible to find beach bars with food (a few offer basic pizzas). I would recommend only Café del Mar if you want to relax at the beach and eat something.
Romanians are really nice people, but the couchsurfing community is almost not existent in Constanta-Mamai.
Safety: Is really safe
I almost never regret going to a place, but I do regret a bit choosing Constanta for the whole summer. If you want to spend some time in Romania I think is better to forget about the beach area and stay in Brasov (my favorite city there) or Bucharest instead.