You're welcome, Dave.
One other point you'll see often repeated on forums, but normally not from people that have actually used both lenses, is that the 100-400 can be soft at the long end.
I thought I show you a few shots taken at 400mm with the 100-400 and let you decide if they're soft. (These were all taken with a 30D - 8.2mp)
Here's a shot of a chipmunk that I shot through a storm door. Notice the flee under his jaw.
1/80s f/5.6 at 400.0mm iso500 (this was shot at 1/80s and I doubt I could have had similar results with a 400L.)
This was shot with a flash and Better Beamer because the feeder was in a magnolia tree and they simply don't allow much light to pass through.
This was shot at the Memphis zoo.
1/400s f/7.1 at 400.0mm iso400
Another zoo shot, 1/30s f/5.6 at 400.0mm iso400 (Another where the IS came in handy - 1/30s)
And here's one, I know I couldn't have taken with the 400L. It's a shot of one of my grandsons taken at KY lake while we were on a pontoon boat. The 400mm simply can't shoot at 100mm.
1/200s f/5.6 at 100.0mm iso400
Hope these were helpful.