Pro's: Freaking tilt-shift
Con's: Limited aperture, manual focus, priced as much as a 24-70mm/2.8L II
Pro's: Freaking 1.4 aperture
Con's: Less versatile than a zoom
Don't get the tilt-shift unless you have a very specific need for it. It's an extremely expensive niche lens that you really should only use for its tilt-shift feature.
I love the 24/1.4L, but I use it as a prime, mostly for its fast aperture in low light and tight spaces. If I'm in a situation where I need to cover lots of different things at different distances, I'd prefer to use one of the 24mm zooms.
If the tilt-shift is in your price range, you should get the newer 24-70/2.8 ii. If you really wouldn't use a zoom, then the 24/1.4 would complement your current glass nicely, but you should at least consider the new 24-70/2.8 ii, with all the great reviews it's been getting. It's definitely next on my list.