I've always used them as I have stated elsewhere here, 2 main reasons:
1 - cold fingers in winter don't use levers very well, but wrist can always rotate gripshift. If this isn't an issue for you you can't be riding in winter! (And forget the gloves argument as they make it hard to use lever shifters too!).
2 - technical singletrack always rapping knuckles on finger shifters/levers, no problem with gripshift.
I never ever had it change gear by accident because wrist rotated accidentally.
Regarding getting gunked up a) what gear system doesn't, ending up in poor performance b) get a RAW powerspring in your rear mech (like I did over 10 years ago and still use!) and this eliminates the problem. This could be used with rapidfires as well of course WHEN (not IF) they also get gunked up
1 - cold fingers in winter don't use levers very well, but wrist can always rotate gripshift. If this isn't an issue for you you can't be riding in winter! (And forget the gloves argument as they make it hard to use lever shifters too!).
2 - technical singletrack always rapping knuckles on finger shifters/levers, no problem with gripshift.
I never ever had it change gear by accident because wrist rotated accidentally.
Regarding getting gunked up a) what gear system doesn't, ending up in poor performance b) get a RAW powerspring in your rear mech (like I did over 10 years ago and still use!) and this eliminates the problem. This could be used with rapidfires as well of course WHEN (not IF) they also get gunked up