I don't think this is a great game, but it was a good experience.
Very short, even with the DLC content you are under 2 hours.
The level design is awe inspiring, the levels are very cleaver/creative without being difficult. It makes you feel smart in the same way Portal did without being difficult.
This is probably the best thing I've ever played on my tablet but the length and lack of difficulty really detract from an otherwise fantastic experience.
The DLC is very much worth picking up, it doubles the game length and the puzzles are more complex.