I have some resevations towards the consept, but I'll refrain from judging some I didn't know about 10 mins ago.
What are your reservations?
The croquet architecture in one maybe not meet the needs of games. But whats about the TeaTime approach inside of croquet. A peer-to-peer "scalable real time multi-user architecture" [http://www.opencroquet.org/Site%20PDFs/Croquet%20Collab%20Archi%202003.pdf] to communicate between objects sound for me interesting. Because, you don't have to leave the abstaction layer of java and do some selfmade binary communication beween your clients. The only issue I do see is security, because peers talk to each other. But maybe this is the only way to develop a MMOG and not have a supercomputer at the backend. To manage all the synchronization.