I use dark pools all the time.  Given that they exist, I see it as in my personal self interest to use them, so that others don't undercut me by a small amount.

That doesn't mean I think they should exist.  I use them because I know others do to, but I do think the free market would be better if it was more transparent.

So... Magical Tux: Don't assume because you see dark pools as being used a lot that means all those users think they should exist.  

And for the record: I *don't* think the limits should be raised.  I think it should be an all-or-nothing thing -- either keep them as they are or get rid of them completely.