Hertford is a lovely quaint town, which has managed to still retain its character. It is officially the capital city of Hertfordshire, although you wouldn't know it from the crowds it draws in! The shops leave a little to be desired, there aren't an awful lot of clothes shops unless you have a lot of money (as the only ones there are rather expensive!).
There are loads of nice places to eat, and there is no shortage of pubs and restaurants. There are quite a few nice cafes as well, with a few by the canal which is nice at the weekends. There isn't an awful lot to do in the town in terms of nightlife, but then again, as I said, there are always the pubs!
The parking is relatively easy, and isn't too expensive either compared to some other cities nearby. The castle and its grounds are lovely to walk around, and Castle Hall often has good shows on.