I've used Irish Moss on almost all my all grain batches. I usually pitch it into the boil around 15 minutes before the end. I never rehydrate it first... Maybe I should start doing that....
The beer seems pretty clear, regardless of whether I put IM in it or not. Flavor and body don't seem to suffer either.
After a year of sitting idle, Andre's All-Grain Brewery has reopened.
Batch #59-Kolsch (Secondary)
Batch #60-Blueberry Ale (Primary)