What I love the most about Rocksmith is that it gets you past the "Suck phase". Pretty much everyone sucks when they start playing. Rocksmith gives you the rest of the band where you can keep playing and it doesn't sound like cats being murdered. The game never gets old for me and I keep playing pretty much every day.
But, that can also be a crutch that is tough to get rid of as well. Make sure that you can hear yourself play like the others have mentioned. And just practice, practice, practice. I think Rocksmith has some decent tools that will help with music theory, like the scale games and session mode.
Just keep at it is really the only piece of advice..