I bought my 17-40 F/4 L years ago, probably 2003 or such at a guess, and have used it for lots and lots and lots of nightscapes etc over the years. I must have tens of thousands of photos taken using it, film and digital.
It's a good performer, can't complain
As mike says f/4 might be a disadvantage, but it's super light and compact as a result, and I lived just fine without f/2.8.
Still going strong, never had a problem, enjoy its robust weather sealing - its been through many a wet stormy sandy beach shoot landscape etc.
I'm not technical with my reviews but would say it's got very little barrel distortion, its vignetting is corrected perfectly by canon in-built software so no problem there, its corner distortion on full frame is noticeable when pixel peeping in a starfield with elongated stars at the extremities, but is better than any other non-fisheye wide I have tried and nothing that would ruin the sale-ability of an otherwise good shot.