Yeah, I had one for a while and ultimately moved to the 24-70 EX.
The 18-50 EX is VERY contrasty, weird - I've never experienced that before, but it was tack sharp and easy enough to use.
By contrast, the 24-70 is a brute of a lens, feels more sturdy and solid, but as a result is heavier and slightly more work to focus/zoom.
Cheers,
James