Wei Dai has written many comments and posts that have some measure of criticism, and various members of the community, including myself, have expressed agreement with them. I think what might be a problem is that such criticisms haven't been collected into a single place where they can draw attention and stir up drama, as Holden's post has.

There are also critics like XiXiDu. I think he's unreliable, and I think he'd admit to that, but he also makes valid criticisms that are shared by other LW folk, and LW's moderation makes it easy to sift his comments for the better stuff.

Perhaps an institution could be designed. E.g., a few self-ordained SingInst critics could keep watch for critiques of SingInst, collect them, organize them, and update a page somewhere out-of-the-way over at the LessWrong Wiki that's easily checkable by SI folk like yourself. LW philanthropists like User:JGWeissman or User:Rain could do it, for example. If SingInst wanted to signal various good things then it could even consider paying a few people to collect and organize criticisms of SingInst. Presumably if there are good critiques out there then finding them would be well worth a small investment.