I posted a message to the developers as I purchased ACR when it appeared on the PC. I have AC, AC2 and ACB also.
I was very disappointed with the 40+ minutes of credits which have prompted me to never go beyond the end cut scene ever again (even if I intend to replay this title). I say that as it seems to be the shortest in terms of overall gameplay and depth than any of the others and yet still costs the same.
It has "frozen" 3 times whilst I was involved with it.
I have a NPC which has a red "x" target on it. This appeared during the poisoning trickster plotline. All of a sudden two targets were highlighted as I chased her: her and this other.
Music: I turn it right down in options but it still plays and it annoys the crap out of me.
Some of the cut scenes are partially silent: sound will be heard then nothing and then sound again toward the end.
Finally, I have the SPECIAL EDITION with a code for extra multiplayer characters and Ezio's ultimate armour. This code will not enter under any circumstances.
Now, all this when presented to UBISOFT, resulted in an automated response then a lacklustre email suggesting I alter my settings here and there and remove tenmporary files, and so on. Steps which I have never had to encounter with any of the previous titles. There was no mention of the code entry problem, nothing about the other issues. Every time I try to respond to the sent emails my messages just bounce back again. After a day or two I then receive another email from UBISOFT declaring that, as they have heard nothing more from me on the matter, they will deem the problem SOLVED.
BULL****! It is not solved at all. Stop dropping your customers into a cyber black hole and you will probably see that none of the problems you get informed of are resolved!