The puzzles start out pretty easy with all the other pieces being just rooks. The difficulty rises at level 16 when a pawn is introduced. It can go up, and never down.
The graphics could be a lot better. The user interface is clunky: it's slow and does not record the number of moves.
Still, I was sufficiently frustrated by the puzzles themselves: they require careful consideration.
Other chess-like puzzles that I've blogged about:
Solitaire Chess - my favorite from this list
Board: Chess Puzzle
Mate in 3? Ok!
Chess Puzzle of the Day
Chess Light - very good
No More Kings
March Simple Chess