I have had a lot of faith in Sistani right from the start. I'm not exactly sure why. Maybe it's because I really do have hopes for the Iraqis, maybe it's because they deserve a break and a kindly cleric would be a great start. A leader who will actually lead them OUT of the wilderness instead of into it.
So far Sistani indeed played largely a positive and constructive role, and he deserves praise for that, but I would never trust a Muslim cleric blindly. He made it possible for Al-Sadr to leave the siege alive, which was one of the biggest blunders in this war.
Also it was especially disheartening when the real pro-Western cleric Khoei, was murdered by the Islamist thug Al-Sadr. And Al-Sadr still is alive.
On a more optimist note, here is a previous thread on a especially outspoken pro-western Shia cleric, who is also Member of the Iraqi Parliament:
http://www.freerepublic.com/focus/f-bloggers/1737075/posts