I did mine as well this weekend, and I had a difficult time getting the old seals out without scratching up the sides of the piston. I didn't put any deep gashes in mine but there were a few noticeable scratches. I doubt they had any effect on the sealing of the piston.
Car doesn't drive all that different, but then again I never had any VANOS failure symptoms before hand (no low RPM power loss or surging at 3k). My VCG was leaking and I figured I should do the vanos seals while I was in there.
Took me about 5 hours but I was cleaning the garage up at the same time as well as doing the front engine pullies and fixing a vaccum line that broke while I was taking the valve cover off.