After reading most of the posts concerning the backfocus problem I wonder if the AF is affected by this. In other words:
If an EX1 shows backfocus problem - does the AF compensate for this or not?
Thanks in advance. (If this has already been covered, please delete thread.)

Should do, yes. But presumably most folks want to use MF for serious work (at least I hope they do!) as if the AF is compensating for a backfocus issue you may well see it "hunting" for focus as you zoom.
Steve