*UPDATE: Got a Real Tone Cable now. Much better. Preparing Rocksmith 2014 review too*
As I was looking ways to learn guitar because I bought a Les Paul recently made me look into Rocksmith, a blend of a learning software and a game that in a sort of way reminds of a Rockband or Guitar Hero but complex and versatile at the time.
I plugged my guitar as I started the game, and it said to me after reaching the main screen I needed a Real Tone Cable as it specified in the store page. It wasn't a problem, as you CAN USE OTHER SOFTWARE to emulate the Real Tone effect so the game can recognise your guitar and then, let you play the game. You have to search the software in the internet and it makes you play outside Steam (that's why I have 5 min played, but I have played several hours) and if you want to be inside Steam while playing, you have to add the shortcut to your Library. Without the Real Tone Cable there is NO WAY to play inside Steam.
I still recommend buying the Real Tone Cable if you have the money to, because the other software can sometimes crash in a middle of a song or event and that ruins the experience of it. If you get the latest patch of the software, it will crash once in a while.

Talking about the music, the game offers a big catalog of songs (including a lot of genres like metal,classic rock, rock, alternative,etc) that grow smaller as you learn them all (but that will take quite a while though!) and a really extense one of DLC that is, in my opinion, somewhat better than the original because you buy the songs depending on your taste of music. I often buy my DLC during a sale since each song cost 1.49$ then and you can buy a lot more.

The gameplay is fantastic. The different modes that a song has include Practice,Perform,Riff Repeater and Techniques Used (and the great Master Mode unlocked after 100.000 points achieved in a song) The most valuable for me was the Riff Repeater, as you have 3 other options inside of it called Free Speed, Leveler and Accelerator (You can also manipulate the speed and level of the section) Those 3 help you to practice different sections of a song without trouble letting you do a first test to know your current level of playing the section, and then giving you 30 attempt to play the section at perfection. Losing lives after lives make you really try to play the section correctly!

At the end, play Rocksmith and you will have a great time as you learn the instrument you love with tons of hours of gameplay. Highly recommended for pros or starters.