3 out of 10 points and not recommendedfocal length, apertureunacceptable corner softness
I tried four different instances of this lens (on an XT). On the first, the focus was off. The center was quite sharp. But on all of them, corner sharpness at f5.6 and f8.0 was much worse than corner sharpness on the Canon 17-85 zoom at f5.6 and f8.0. We aren't talking barely perceptible differences, we are talking thin lines disappearing entirely. Wide open, the performance was even worse.reviewed November 6th, 2005
From a comparatively heavy EU 450 standard prime lens, I expect that it at least matches the performance of a consumer-grade zoom when stopped down to f5.6 or f8.0.
No lens is entirely useless; this lens may be useful for portraits (be sure to put the face in the center and crop later) and getting very shallow DOF effects (where corner softness usually doesn't matter).
As a general-purpose available light lens, the Canon 35/2 is a better choice: sharper, lighter, cheaper. The extra f-stop on the 30/1.4 isn't all that useful for general purpose photography anyway because of the shallow DOF. That's compounded by a generally inconsistent focus from this lens.
Another option you might consider is the Sigma 24/1.8; it is a much better performer than this lens; unfortunately, it is also even bigger and heavier.
It is possible that there have been better batches of this lens. Some of the sample photos on the web have much better corner sharpness than what I saw. I have to admit that I would still love a lens like this, and I keep trying them out when I see one at a dealer, but no luck so far.