Crazy, I am unaware of any type of added latex grip that lets four of your fingers touch the stick while guarding your thumb... unless you're talking about adding the latex to your thumb, haha.
Do you have a picture of this device?
My point is that more data feedback from the bass means more information to help me play. The tangible vibrations give me information about volume, attack, decay, pitch, grippiness, slipperyness (which translate into timbral information and bow stroke information). Ever play with earplugs in? It opens up a whole new level of intimacy with your instrument when you have to /feel/ everything that both it and you are doing. I find that feeling how the entire system /feels/--in addition to listening--gives me a more complete understanding of how to use my body to get the sounds I want.
Yes, of course it's all about the sound you're hearing, but you can't stand 100 feet away from your bass and play your bass at the same time, so you don't really know what it sounds like.... Sometimes you're in sonic situations where you need to make a noise but you can't hear yourself through the murky soundmass of the ensemble you're playing with--especially given your location relative to your sound source (above, not in front of, the bass).
In any case, I personally find that a rubber grip is not a negligible difference in the playing experience--a small difference, yes, but not negligible.
-Trevor
P.S. I fully concede the fact that my experiences in this matter could be all in my head and, if we were to conduct some controlled experiment, be easily proven wrong.
I hardly think that a latex grip cuts down on feeling the vibrations. Only the thumb is touching the latex and there are still four other fingers touching the stick. I can feel vibrations just fine with a latex grip. the benefits of the latex far outway any minor decreases in feeling the bow vibrate, if there are any at all. But that is just my opinion, and I don't think that feeling vibrations in the stick are that important to over all playing.