My duty gun, a 23 RTF2, has the gills, serial number PET 5XX, and a fired case dated in May 2010. My personal 23 RTF2 doesn't have the gills, serial number PGA 8XX, and has a fired case dated 2/11/2010. Go figure.
I think the gills give the guns a lot more character, but frankly I find the straight serrations a lot more functional.
Mon: Do you carry chambered?, Tue: Can a cop write a ticket without his hat?, Wed: Should I carry a spare mag?, Thurs: I got stopped without "probably cause"., Fri: Will there be a Glock Carbine?, Sat: Why the GAP hate?, Sun: I hate the GAP.