17-35mm Canon vs. 16-35mm Canon?

I have an old 17-35mm Canon L lens from the late 90's. Still in great condition cosmetically and photographically.
However, whenever I see a rebate for the newer or newest version of that lens (now a 16-35mm, of course), I wonder if I should consider replacing my old lens with the newer one.
Besides better weather protection and a larger filter size, what changes would I notice with the newer lens? Any reason to change?
Thanks.

I guess to really make a step up consider buying a 17mm TS-E if you do landscape or architectural stuff (otherwise i'd recommend the 24mm TS-E which i absolutely love, but even if your 24L and the TS-E is for different purposes i guess its still redundant having so many overlaps)

Thanks for the suggestion!
However, I'm just trying to determine whether or not to replace my 17-35 with the newer (and improved??) 16-35mm.
Though I have thought about the tilt-shifts from time to time. They really don't fit my needs at the moment.

http://www.fredmiranda​.com/17_35VS16_35/

I have a nice copy of the 17-35. It uses 77MM filters and I dont crop that far into a pic to see the differences. Fred is in well past 150%.....WTH cares what it looks like at 150%. I dont shoot wide as much as i probably should and find that for most of my needs 24MM is plenty wide. But, for those times when i want to be wide, 17MM is very wide and I find that at F/2.8, mine is pretty dam sharp.

The other factor is costs. I got my 17-35 from a guy that just didnt know what he had. Got it 4 yrs ago for $550.00 and it was like new. So for me, $550.00 v/s $1300.00 was a no brainer

I have not upgraded since. I get great results with my older 17-35.

umphotography wrote in post #16734694
I have a nice copy of the 17-35. It uses 77MM filters and I dont crop that far into a pic to see the differences. Fred is in well past 150%.....WTH cares what it looks like at 150%. I dont shoot wide as much as i probably should and find that for most of my needs 24MM is plenty wide. But, for those times when i want to be wide, 17MM is very wide and I find that at F/2.8, mine is pretty dam sharp.

The other factor is costs. I got my 17-35 from a guy that just didnt know what he had. Got it 4 yrs ago for $550.00 and it was like new. So for me, $550.00 v/s $1300.00 was a no brainer

I have not upgraded since. I get great results with my older 17-35.

Thanks!
A good recommendation for me to stand pat with the old version. Besides, I like that it has 77mm filters, is smaller, reliable, and in great shape. In other words, no dramatic improvement that's enough to compel me to make a change.
However, I've seen that "Fred" review before. And it's for the older version of the 16-35mm. It's since been upgraded again!