Row-level locking and XtraDB Cluster
InnoDB works the same in Percona XtraDB Cluster when you look from the single node perspective. But when you allow writes coming to multiple nodes, you may face conflicts. So either you keep doing writes to only one node at a time (like if you had only one master), or you will adapt your application to avoid conflicts.
This may be helpful for you: http://www.percona.com/blog/2012/08/17/percona-xtradb-cluster-multi-node-writing-and-unexpected-deadlocks/