For starters, head over to Keen and Graev for an interview with Mark, who also answers more questions in the comments.
My biggest issue with CU is that Mark made WAR, and for a long time I didn’t get the feeling that he understood and accepted why WAR wasn’t as good as it could have been (can’t call it a failure since it was profitable, but that just makes it a weird title that was profitable yet isn’t online anymore). He would always state it launched early as a major problem, but IMO that wasn’t really it. Even if the game didn’t have the technical issues it had with sieges crashing and massive lag in RvR, it was still flawed.
Once you hit the level cap, got your gear (not that difficult), and had seen a capital siege, you won WAR. There was nothing else to do. Not from a character progression standpoint, or a RvR perspective, or for a guild. That, IMO, was the critical and core flaw of WAR. And yes, I think its safe to say most players never hit that ‘win’ mark due to other issues, but ultimately if all of those were fixed, WAR still didn’t have the core design to keep it going.
That remains my primary concern with CU, but based on recent info and what Mark has said, I’m not as worried about it, and I know that if Mark and company are able to get that part right, CU is indeed going to be awesome.