I have had a TSIIIa on my TS2424 since October '99.
It is wonderful, I couldn't ask for anything more. Since the TS2424 is a left-tilt saw, there isn't any reason to move fence left of blade. Therefore, I mounted the stock Incra rails pushed over to the right. I can slide the "bridge" the fence mounts to 18", giving me a 50" width of cut when needed.
One thing worries me a little. If you are very tight on space, you must consider the extra width the Incra consumes when opened wide. If you look at a picture of the TSIII, like this:
http://www.incra.com/TS-III.gif , you can see the center bar sticks out past the rails. When mine is opened all the way, the saw is around twelve feet wide. This is the biggest disadvantage to the TSIII design.
Should you decide on the Incra, don't try to cut the Ridgid splitter/blade guard to fit around the rear rail. Tried that, doesn't work.
Dave