Used it since my film camera days, then for 10D and 1DmkII. Although not on par with 50mm f1.4 and 85mm f1.8, it has good color and contrast, and pretty sharp when I step down a little. It also focuses pretty fast.
I found that using this lens, 85mm f1.8 and 10d are a great high quality compact system.
The only complain I have is that its focusing sound is very noisy, which is not good for wedding photography...