I like this game, but I don't love it. It's short and easy, with "short" being good because "easy" made it become slightly boring by the end and any longer would've been dull.
I'd like to make some suggestions for the future (or version 2):
1. Make use of the right mouse button. Clicking three times to rotate in the direction opposite of the default is no fun. IMO, the left mouse button should be counter-clockwise, while the right mouse button should be clockwise (i.e., what the left mouse button is now).
2. Add crossroad elements. You might even want to consider more complex ones.
3. A bit bigger maps. Not too big, as it would become too hard on eyes, but double the current size should be enough.
4. Keep rotations consistent. That one step where it rotates back by 3pi/2 back instead of going further for another pi/2 is confusing in the beginning and somewhat annoying later on.
5. Not sure that it's a good idea to allow - and even insist on - having pipes unconnected to the sources.
6. A bit more engaged graphics would be nice.
7. Some for of menu (with "sound on/off", "pick level", etc.) would be useful. In the long run, it could lead to having a levels editor with shareable user-made custom levels.
This "Pipes" game clone really has some nice potential, with my favourite part being that it has no time limit. I do hope you go for an improved version 2.