LensHog.com

This is one of my favorite lenses. Optically, I'm not sure there's anything that will beat it at 135mm. It's sharp edge to edge wide open with no visible CA whatsoever. Review to come shortly.

The only real competitor is the Samyang 135mm f2. Even better image quality, cheaper, but not as good build quality, and the focus tends to have a grainy quality to it.