Another thing you might want to think about is that you cannot micro-adjust your lens with the 60D and it could be that part of your unhappiness with your current lens is due to a need for your lens to be micro-adjusted or calibrated to your 60D. YOU/WE can calibrate lens for the 50D, 5D?'s, and 7D as well as the upper end pro bodies but not the 60D. If you get a L lens and your sensor is off, the new expensive lens could just as well need calibrating and you'll need to send the lens and camera to Canon to be calibrated.

A lot of uhh'ers who shoot the 60D will come to their defense but if you google for complaints about focus problems with the 60D, you'll get way more hits than you'll want to read. Some of those images you've seen that failed to impress you may be soft for a known reason and the owner doesn't know the difference or that the problem even exists or that there is a solution and what that solution is. Personally, if I owned a 60D I'd buy a L lens first, if it's soft, do the calibration thing with Canon and start looking for another body to trade for with people like KEH, Adorama, B&H, or Canon even, maybe a refurb 7D.