This game is fun and addicting, but it has some major flaws.
First of all, the difficulty curve in this game is pretty wonky. Now, I'm not sure if this is because I got used to the game as I progressed, but I felt that some of the later stages (especially from world 2) were incredibly easy when compared to the earlier ones. The difficulty ramps up again towards the end, but you'll still find that it varies greatly from stage to stage instead of following a steadily rising curve as you would expect.
Second, while the level design will overall test your skills and reflexes, it can be a bit repetitive and sometimes very frustrating. The game will resort to artificial methods of increasing the difficulty by placing obstacles and items at very awkward positions, and since a single mistake will take you back to the beginning of the stage, that translates into annoying trial-and-error gameplay. If you don't mind having your patience tested, then you should do just fine.
And last but not least, the game has a motion blur effect that, as far as I know, cannot be disabled. I guess they chose to use this effect to give a good sense of speed and movement, but it would have been nice to include an option to disable it. Not only that effect is going to tire out your eyes if play this game for long periods of time, but it might also cause you to fail at certain points of the game because the game's art style doesn't stand out very much — obstacles and items tend to blend in with each other, it's hard to tell them apart sometimes, and the continuous blur doesn't help one bit.
The game is still worth a shot, if you're feeling adventurous. The difficulty is insane and rage-quit inducing, and finishing a tough stage can be very satisfying. Sadly, however, I personally think that the flaws outweigh its qualities. I recommend you try the sequel, "Runner2", a much better game in pretty much every aspect.