A few follow-up notes:

For waterfalls, I prefer to shoot at f/8, never smaller than f/13 due to diffraction. Go to f/13, ISO 100 and you're still at 1/100th or so in sunny weather, 1/25 on a moderate day. Even down to f/22 it's only 1/10th. The shot below is 1.3 seconds, and I always try to get to 1 sec. or slower to get the white cotton candy effect. That's 4 stops on an average day. I wish I had gone higher than a 3 stop ND, but I can stack an ND and CP, which is worth about 1.5 stops.

A 24-70 or 24-105 won't work with a Canon 1.4TC - it only works with 135+ primes and 70-200+ zooms (I think - you can Google the details). You could go with a Sigma or Kenko 1.4TC, which fits any lens - I haven't compared their quality to the Canon.

I always have hoods on my lenses, but I took a look at the filter on my 70-200/2.8IS today and there are two small scratches in it. So I can't agree that they are "worthless". I'd rather buy a new B+W MRC UV filter (don't buy a cheap filter) than have a scratch up expensive lens.

It also intercepted my daughter's flying oatmeal a few years back.

http://richs.smugmug.com/photos/120888983-L.jpg