I just sent my camera (5DIII) and lens (24-105L) to Canon for regular maintenance. I told them to take a look at the lens because it was particularly soft on the edges. They came back to me with a manual autofocus issue and they have to change the USM. It would cost me $300. I payed this lens $450 4 years ago, I am not sure it is worth it.
I would no mind injecting a little more cash to get a better/newer one. The f2.8 is out of budget and I don't think I would like the range too much. 70 may be a bit too wide.
What do you think? What are the other options?