guitars

It does feedback if you hit the wrong note (or it thinks that you hit one), but it doesn't really outright tell you about your timing and will accept some horrendous timing if the note was right. In fact that is one of the major points people seem to mention as its' drawbacks.
Although I would personally say that Rocksmith has been pretty pivotal to my timing (along with recording), since at least for me it multiplied the time I was playing to a rhythm of a background track. The game allows you to loop and slow portions of songs that you like and play the parts on repeat against the original song with a relatively nice and fast interface, way faster than doing it yourself on a DAW. And that little convenience has me playing to rhythm way more than I would otherwise at home by myself, and especially work on hard parts slowed down.
(Can't stop editing this post lol) Oh and possibly worth mentioning, my experience is with the 2014 remastered edition with popular mods installed (RSMods, RS_Asio and CDLC), can't say much about the new version