Hi TD-Max,
The gel that is used in the Talalay GL fast response is a phase change gel. You can read some of my thoughts about regulating sleeping temperature in post #2 here. There is also more about the different types of gels that are added to various foams at the end of post #4 here.
In terms of their cooling properties … I think that in combination with the other factors that affect the temperature of a mattress … the different forms of gel can be an incremental benefit for some people but the claims about them are also overblown in the current marketing frenzy about gel foams in general.
The only real drawback is that the material costs are higher and this would be wasted for those who don’t notice any “real world” benefit.
As a part of the bigger picture that affects temperature regulation … they will probably make some difference for some people who tend to sleep hot (although talalay latex is already the most breathable and coolest category of foam material).
Phoenix