I have a 19 with the RTF2 texture and fish gill slide serrations. Along with that, I also have 3rd gen 34 that has the regular 3rd-gen texture. These are my first and only handguns are were both purchased within the past 5 or so months, for what that's worth.
I ordered the 19 with the RTF2 after handling a 17 with the RTF2 and shooting a regular 3rd-gen 19. I really liked how grippy the RTF2 finish is and wanted that on a 19. When I actually picked up my 19 at the LGS, my wife went along and absolutely did not like grip texture. The woman who processed the purchase/background paperwork said that from what she'd seen, men tended to like the RTF2 while women universally detested it. For what that's worth.
To me, the RTF2 finish makes the gun stay put in my hands, whether shooting one- or two-handed. I don't find it uncomfortable even after shooting a few hundred rounds in a range visit. I have had several friends (all non Glock shooters) try both the 19 and the 34 and all of them have remarked on how solid the 19 feels in their hands compared to the 34.
I shot the 34 an IDPA introductory class in May. The range portion of the class was outdoors and it rained pretty heavily during portions of the shooting segment. The 34 itself performed well but I sure wish that it had the RTF2 texturing. The 34's texture is "acceptable" but it's not like the more aggressive purchase of the RTF2's texturing. Put another way, if the 34 had been available with RTF2, I would have bought that instead.
There are some drawbacks to the RTF2. I have a CHL and I do find that the RTF2 will grab onto shirts when moving from a seated to a standing position. I don't think it's that big deal and I've learned to simply give my shirt a slight straightening tug when I get out of a chair or car. I have read articles saying that some LEO's have reported that the RTF2 has worn holes in duty shirts.
Overall, it looks like Glock feels that the RTF2 was a bit too aggressive as the Gen4 guns have a less-aggressive polymid shape and density on their grips. But I do honestly prefer the RTF2 myself. And as an aside, not all of the RTF2 guns have the curved/fish-gill slide serrations - some do have the regular straight serrations.
I hope this info helps.