I spent a solo vacation for 4 nights at Lanta Il Mare. This hotel is right on the beach, at the end of a strip of hotels off of Klong Nin Beach.
Overall it was a very pleasant stay. What made it quite nice was the service. Hotel pickup and dropoff from Krabi airport was quite easy, and the receptionists are warm and friendly and speak good English. The restaurant food is good, and the staff are accommodating; for breakfast, they normally cook American-style breakfasts, but I asked for a Thai breakfast, and they fulfilled my requests. Plus, if you walk 15 minutes, there are plenty of seaside restaurants and other hotels where you can find food.
The hotel itself is clean and nice, although it is worth paying extra for the sea view; if you don't your view may very well be a wall. The pool seemed fine as well, but I am more of a beach person, and it was clean and nice.
Overall, a Lanta Il Mare is a great choice for a relaxing holiday!