I have always had Scalextric track, but the Ninco track is supposed to be good and you can get adapters to mate the two. Th good thing about the Ninco track is the extra width, but the Carrera track is slightly wider still. I think the hard plastic tracks are better than the Scalextric - try looking down a long length of Scalextric straights after they have been used a few times and they are VERY uneven. Given the choice I would go with the Carrera if I had to set it all up over again.
Try this site -
http://www.ncphobbies.com/132help.html
The cars themselves are getting to the point of being great static display models as well as slot cars. The best I have seen to date are the 'Fly' cars. They have some superb classic Porsche racers, 908's and 917's.
That said, alot of the other manufacturers have been catching up the last few years, but I'd still look at the range of models from 'Fly'.
Look at this site -
http://www.scalemodels.co.uk/ - I know they're inthe UK, but I have used them before and they know what they're doing. They also have a lot of the old 'collectors cars' to look at just in case you want one the same as you had when you were a kid!
Another thing, I would advise staying away from open-wheel cars for a while. They are easily broken and just don't stand up well to 'wheel bashing' which is inevitable in slot car racing.