anyone used them to fly?
Yes, we flew them from Florence (FLR) to Amsterdam (AMS). Budget carrier, basic, no frills. They charge for on-board drinks other than water, which is not surprisingly, overpriced. Plane was typical of the smaller craft used for short hops and I believe was 3 - 3 seat configuration. Nothing special, nothing horrible.
We had a check-in fiasco, but that was the fault of Northwest, not Meridiana. They were apologetic, and did try to call NW but it was the middle of the night in the U.S. They perhaps could have done more in terms of customer service, but I don't hold them responsible since they didn't cause the problem.