I can't say I've had a lot of experience, as I've only had my 24mm T/S for a week so far. Prior to purchasing I suffered the same thoughts... however, I decided with the Canon for reasons of simplification.
I can't say I've noticed the chromatic fringing on the edges with mine though... and personally... I've found it's performance to be suprisingly good... When I had originally ordered it, I thought "what have I done? Maybe I should cancel it, and buy the Nikon or that other brand?" Especially when you read the reviews on places such as FM. You'll see it's not received a lot of good reviews, and it's overall rating is pretty low.
That said, the on I have is a very good lens, and the only thing I can fault with it, is the lack of accurate exposure when shifted or tilted, especially towards the extremes. The saving grace of this though, is the fact that T/S lenses aren't really the fastest lenses to use.
For me though, it's become my 24mm prime to. Unshifted, and untilted, it's the sharpest lens I've ever used.