Tara's[/url:dk7kbren] was the first one I remember, back in 2008, won by Bigears. Hilden ran one at their festival the following year[/url:dk7kbren], Delboy beating Bigears into second place. OghamBrew ran a few fairly big events[/url:dk7kbren], though their last one in August 2009 was the first of them that was really open to the public.
The NHC and Abbeyleix ones will be the first run by practising home brewers, which I think will make a big difference.