10D Autofocus/Exposure Problems

I realize that I've got 2 subjects here ... but they are the ones that are haunting me.

The camera was a few months old when I sent it back re the above problems. Came back with notation that they had replaced a "worn shutter" and brought it up to "factory specs".

After a month of use, I'm beginning to see examples of inconsistant exposure problems again. Haven't had the chance to to challange the autofocus issue yet.

Seems to me I've seen earlier posts re the autofocus, but couldn't locate them.

Is the AF in fact a common problem with the 10D. If so, has anyone gotten permanent resolution?

Lenses used are the 16-35 EF 2.8 USM, 24-70 EF 2.8 USM and 70-200 EF 2.8 IS USM.

Any input before I go back to Canon would be helpful.

Thanks