8 out of 10 points and not recommendedcheaper than canon's 24-70not that much cheaper particularly in the UK
I'm using this lens on a 5D2 and I find it to be pretty sharp at f2.8 and seriously sharp from f4 on.reviewed March 30th, 2009 (purchased for $1,034)
I've not noticed any CA or purple fringing with this lens so far and the distortion at 24mm seems minimal.
The only thing that lets this lens down is the vignetting on a 135 frame is pretty bad and does not really disappear at 24mm. This is however really easy to remove when processing your RAW.
my copy is not particularly good at min focus distance and I did have to dial in focus microadjust to stop it front focusing. (it also did this on my 20D & 40D so I'll be sending it for recalibration soon).
filter thread not a problem since 82mm hoya CP's are pretty cheap from HK.
If this lens was $150 cheaper than it currently is it would make a great deal of sense but because its not that much cheaper than the canon L version I would advise unless you are really skint to save the extra and get the canon to avoid any focus problems. I was seriously skint hence the purchase lol