I've had the following (I'm a bit ADD when it comes to optics):
Vortex Strikefire I: Cheap, decent, looks nice, worked okay.
Vortex SPARC I: Cheap, decent, smaller size than the Strikefire, brighter dot that the Strikefire, a bit more expensive.
Lucid: Not as cheap, looked great, had multiple reticles to choose from, it mounted pretty weirdly and was always coming loose. In the end I hated fiddling with it. Next guy might have solved the mount issue, I dunno.
Burris Fastfire II: Good precise dot, smallest, provides widest field of view, but harder to acquire as it is small. Definitely more suited to pistol.
Holosun HS403G: I just picked up one and haven't fired with it mounted yet but so far the build quality is decent, the dot seems fine and bright enough and it has a neat auto-on feature based upon movement. You turn it off and then it will come on if you snap your gun up or shake it. It does have a noticeable red tint to it.