I think the TS-E 24 being the best 24mm is pretty subjective.
I think the Nikon or Canon 24mm f/1.4's are better, they bring in over 4 times the light the T/S's do, can isolate subjects much better, and have AF. I need that for the weddings I'm able to shoot analog on and my fastest film is 400 (at 200). At 24mm, I'd MUCH rather have f/1.4 than T/S, regardless of distortion.
Different strokes, different folks. Also if you can afford (which I assume you can considering how expensive the 24 is), instead of getting the 24TS, get a 4x5 view camera with a 90mm. I can't think of many uses for a 24TS outside of landscape/architecture, and Large Format is much more suitable for landscapes/architecture than the pithy 35mm format.
Now if you're shooting with a 5DII, well that's a different story..