I think I agree with you, maybe a bit better for indoor work with f3.5, but I believe that it is all new glass and build, old one size 83.5x81 77mm filter, new one is 87.3x88.2 82mm filter. I don't own a filter yet, but maybe when I get into Landscape I will be changing my mind ?
I agree with you there Pete -I often find my 17-40 too wide and that is when the 70-200 comes in handy. I think the ultra wide's are more useful for close-ups of buildings and things where you are restricted as to how far away you can stand. I must admit I am not a big fan of some of the ultra wide shots that have a strange perspective but I know a lot of people do like these lenses.I don't like landscapes shots taken with it as the ultra wide angle tends to flatten the shot, dramatic landscapes loose their impact IMO. I don't shoot landscapes often (must try harder) but when I do I tend to reach for my 70-200.
I must confess that I don't see the need for a faster aperture on a wide angle lens, most of the time you'll be wanting lots fo DOF so will end up stopping down a fair bit.
Here's a few images with the f3.5, be gentle I am still learning.