Since the first details of PCM11 were revealed in a very, very short Q&A back in January, we've pretty much been left guessing. A few features were revealed by the official screenshots, thanks to our observant members, and Focus has now decided to reveal all the main changes between PCM10 and PCM11.
Graphics-wise, as we've seen on the screenshots, a lot has been changed in the rider model. You can now see the "individual psysique of each rider" (or at least you have the possibility of "enabling" this). Some new 3D-equipment has been made, and - again, as we've seen - it's coloured in the teams' colours. There's also plenty of stuff for the stage makers, including new terrains and landscape elements.
Speaking of stages -- PCM10 came with way too few stages, but PCM11 increases the number with 65 %.
The gameplay, however, is the most important part of PCM11, so obviously, a lot of work has gone into this too. As mentioned, the riders will no longer pass each other (although it can happen, as Clément Pinget said, just not as often as in previous games), the sprint AI has been revamped, and there's also a change when it comes to the Mountain Jersey AI.
Team sponsors can now change (e.g. Saxo Bank withdraws its sponsorship, is replaced by a new sponsor), and for this feature, there's also added some interaction between the manager and the sponsor. For example, the sponsor can have regional or national priorities that you have to pay attention to.
Lastly, it seems that Cyanide has decided to get rid of its GameCenter client. Instead, you connect through the game - like in CyM2, if anyone remembers that.
You can read the full announcement by Focus here.