Upload & Sell: Off
I shoot everything on a tripod, MLU, 2 second delay, LiveView, with a remote. My set up is as stable as can be.
If this is the case (especially LiveView), I'd guess you have a lens that has some internal problems. Yes, I'd recommend the f/4 IS (I've used it for years), but what to do with the old one? It doesn't seem right to sell your problem to someone else, unless you've made full disclosure. You may want to sent it to Canon to get the apparent problem fixed, and then decide to either keep the fixed lens or sell the repaired lens and go with the IS version.