Well, like most dental work, there's discomfort to put up with, but other than that it's really nothing to worry about. It certainly shouldn't hurt-if it does then you need more local anaesthetic-except for a small sharp pinch when the nerve is removed. Personally when I had one done I was just intensely relieved to be rid of the awful toothache I was getting.
The initial root canal should be fairly rapid-about half an hour or so, but the final stages of sealing it and filling it can take several more visits as it has to be shaped for the filling, so you may get it temporarily filled at the first appointment and then have to go back later. It'll also take more time if you need to have a crown fitted as often they're porcelain and so individually made so they need to get a mould of the tooth and have it made.
I had my root canal done as an emergency which was very quick, but the cleaning up and having a crown fitted took a couple more appointments after that.