hcat and Bseabob,
I was feeling guilty because we've never tipped in the Normadie, thinking the $25 charge was to cover the tip. I had a peek at the Celebrity website FAQ under Prepare to Sail (search on specialty) and they said:
"There is a cover charge for dining in the specialty restaurants onboard Constellation, Millennium, Infinity, and Summit. This charge is a per person charge that will be posted to your onboard signature account (This covers gratuities). "
So now I don't feel quite so bad about not leaving an extra tip. Although of course the extra would be appreciated, I'm sure, and the service WAS outstanding. (Now I'm feeling guilty again!)