I like the Heath for a breath of fresh air in London. One of the beautiful things about the metropolis is the incredible amount of lush green parkland in and around the city.
The Heath is a good place for a stroll, viewing of the city, etc. The nearby Highgate Cemetary is very cool to stroll through on a tour or on your own also. Sometimes they will let you into the catacomb like crypts and that is a real eye opener. The pubs are fair, but not what I would call out of the ordinary. The area has a nice atmosphere so after a stroll on the Heath, a pint or several may taste even better than usual.
If you have not been yet, I would try and squeeze it in.
Mike