I was in the Merchant's Arch place yesterday. In addition to the Carrig lager (as listed in the Beoir Directory), they had a significant range of Irish brews on tap including O'Hara's stout and Red, Metalman Pale ale, Galway Hooker (though were out of it yesterday), Trouble Brewing Ór, Crean's ale, and "Rovers red ale" listed as being from Offaly. There was also an 8 Degrees tap but I forgot to check what beer it was.
As others have said in the past; it's a nice place with a nice view but pricey with no prices shown anywhere that I could see. Two pints of Metalman cost €11.60.