I have the old, heavy version. about six months ago it became undependable in autofocus. I can still set to manual and use it, but doing a lot of shots with three very young grandkids who move around pretty fast (ages 1, 2, and 4). Not sure if it is worth having it fixed, and if so, where.
I had one a long way back. It was a $300 - $400 repair. A few years later I had the same issue and bought the newer version, 24-70 'E'. The repair was good for several years, so it may be worth it depending on the cost.