Currently QuasarMX is the only music player that decently supports gapless for Meego-Harmattan. Though it's not free, it's actively maintaned by the dev who owns it, and he also posts here. It's feature-filled and performs very well.

Though gapless transitions are not absolutely perfect (but are pretty darn close), he has mentioned that he is exploring a way to make it even better.

I hope he also ports this to sailfish and based on his track record of porting to other platforms, I am optimistic.