Someone asked me this morning if I would use the YouCat. I said no. I do not need to go into all the reasons, and I think there are problems with translations. One can read a good review here. If anyone has information on updates which correct the problems, please comment.
http://catholicinformation.aquinasandmore.com/2011/08/12/theological-problems-with-the-youcat-have-forced-us-to-discontinue-selling-it/
I personally would start with the Compendium of the Catechism of the Catholic Church, and as a teacher who uses "original" sources, I would be using encyclicals and basic texts rather than the YouCat.
By the way, the recommendation of use for the YouCat is that it is for ages 14-17. I disagree. A teen can use the Compendium and the CCC. Why do we dumb-down truth?