Well its better than Bug anyway.....
Clockwork Knight plays just like any old 16-bit platformer would have, and in fact has a graphical style similar to that of Toy Story on the SNES and Megadrive. You walk along the 2D playing field and avoid the 3D polygonal collapsing scenery and whatnot. When you want to kill a bad toy you poke it with your key and wind it up till it pops.
So yeah the gameplay isn't too deep, and Clockwork Knight is also very short. This wouldn't be a bad thing except the game is incredibly easy to complete even on your first try so it makes the whole thing only worth an hour or two of your time at most. Despite this though the game IS worth that hour or two of your time simply because while it lasts its a pretty decent game that has some good music, nice graphics and you will probably remember the boss fights for a while as they are quite inventive.
While it certainly isn't a game id tell you to spend money on while you’re saving up for Radiant Silvergun or something, if you find it really cheap it is probably worth a play through as its a lot more pleasant than the annoyingly lame Bug!. After all, any game where you fight a giant Transformer has to be worth a go, right?...