Yep. We left Castles & Crusades. As a group, most were satisfied with 3.5, but the DM was a little burned out on it. Myself, I'd hit a creative wall. So, we went to Castles & Crusades. It was fun for a while, but we made some basic mistakes, some from the DM's end in choosing material that didn't adapt well, and some discord in the group.
So, we ditched C&C and went 3.0. Yep, 3.0. Gave Dragonstar a go. Well, that was short-lived, so we rebooted in Rifts. That didn't go so well either. We refreshed with some Settlers of Catan and decided to have a group vote on a new campaign, with a fresh look at genres and systems. Well, the vote of the group was unexpected, at least to me, but delightfully acceptable. No one in the group wanted to go back to 3.5, and no one wanted to learn a new system again. So, we went back to Castles & Crusades, having learned from our previous mistakes. The new game is going dandy.
I know that doesn't exactly fit the OP's criteria, but technically we DID try C&C and didn't stick with it. But we eventually made our way back to it, and are quite happy with our game again. This one has legs.