If you are after good scottish food then Stac Polly is a safe bet, although it is wise to book ahead. Deacon Brodies has already been mentioned and I would second that for a visit. If you fancy a Haggis Supper take away, then then Kingfisher at the top of the grassmarket (bread street) is the Best in my opinion. Not Scottish I know but the Guru on Dundee street is great for Currys and as it is tucked away out of the normal routes it is never very busy.

For a bit of a laugh, try Jekel & Hyde ( fredrick or Hannover street I think) for a few pints and then try to find the toilets! They also do food, but I can't say I have ever eaten there while sober.

:o)