They have the same looks. I personally don't need 2.8. I have another lens with F1.4 and if I need it I'll use that.
This is going to be used for outdoor nature & wildlife.

I'm going to be getting about a 400mm in the beginning of 2009.

Anything lower than 2.8 is too slow for action shots, got this info from a friend of mine

That's what I have read in thephotoforum as well, can't just find the posts about the 4.0 L and 2.8L but a few of the pros there said that 2.8 is a must for those who are into action or nature photography

Yeah. Makes me doubt about getting that 10-20mm Sigma wide angle lens :S

hmm well unless you are going to take whole a lot of low light photos handheld or action or nature photos with an ultrawide lens the narrow maximum aperture of that sigma lens shouldn't matter too much. Unless you want to reconsider and check out the Tokina 11-16 f/2.8 lens

Review:
http://photo.net/equipment/tokina/11-16/

thecamerastore:
http://www.thecamerastore.com/products/catalog/wide-angle-lenses/tokina-atx-11-16-f28-canon-mount

This post was edited by Futurama on Dec 16 2008 08:38pm

they are supposed to be leathal, and they DO look good, coz they have one really wide end!

and thats what all the pros use so you cant go wrong!

Beatrice? Lol, that's the name of my parents' dog.

Depends how much light there is.

nice camera
but ur ugly as fuck!
picture is ruined .. cuz ur in it

lol another stupid multi in desperate need of higher post count. I'd bet 100 bucks on that this guy is going to belong to the Banned group within a week