I found the staff at the Mercure to be extremely helpful and friendly. I stayed at the Mercure for two nights - one on my way to Mana Island and one on the way back to New Zealand, five days later. Even though I'd only been there for one night, the staff all recognised and greeted me - and one woman even noticed that I'd developed a tan!! It makes a huge difference to your stay when the staff are that great.
I hadn't initially realised that the buffet breakfast was not included in my booking - something to ask when you reserve your room. However, for FJD 19.50 (about GBP 7), the breakfast was more than adequate - including the dedicated egg-maker (eggs any way you like them!).
I had different rooms for each night that I stayed. The first night I had a ground floor room which overlooked the pool area - although the locks etc worked fine, it probably wasn't in the best location for a female travelling alone, but there were no issues - just from a state of mind perspective. Amenities in the room were as expected for a hotel in its class.
However, the room I had on my return visit wasn't quite as nice. There were large, significant chips in the enamel in the bath, which doesn't affect the shower itself, but just looks like they need to spend some money to improve its appearance. But fine if all you do in your hotel room is sleep and shower.
All in all, a good hotel for what you're paying, but don't expect a luxurious stay. I can't comment on the pool or the meals as I didn't use the pool or the restaurant (aside from breakfast).