Its size and weight is comparable to the 28-105 f3.5-4.5 so it's very compact and light.
The optional barrel hood is quick to mount/dismount with 2 quick release tabs on the side. Can be reversed on your lens for easy storage. Not the best of lookers but, you get over it pretty quickly when you see the results.
Operation: AF is very quick. Very similar to the speed of 17-55 f2.8 IS - which is damn quick! Silent and accurate operation allows this lens to sit on my 30D alot longer than any other lens...17-55 included!
The rest you've heard before: sharp wide open...contrasty and sharp all round...great in low light...great in low light!
Portrait shots of 2-3 people (head and shoulders) = amazing! You're not in their face - unlike the 30mm 1.4 or even 50mm 1.4.