re: Sistani has been laying pretty low lately.
He is well aware that he stands a pretty good chance of doing very well under the political process, and sees no need for violence. There are a LOT of Shiites, and if he is moderate enough to convince the moderate ones (and there are a lot of them, too), he has a pretty good future ahead of him.
It's no coincidence that most of the violence is being undertaken by Sunnis, which used to rule Iraq and don't have the numbers to rule it outright under a democracy.