In reply to nufkin:
Agree. For what it's worth, I have the BD spinner leash on my vipers and have not had any problems with them unclipping. May well be because they gate in the "karabiners" is quite hard (dont know if it will get looser over time. for now I quite like it). I say "karabiners" as they are not like the Grivel one which has real krabs, they are more like metal accessory krabs than anything else.
On this point, the Grivel, if I recall correctly, has locking krabs so the unclipping should be even less of an issue.
Lastly, in my limited experience being able to unclip the axes easily at the belay helps quite a lot as if you are swaping hands during the route for any reason you may find that the leashes get tangled in the rope (when seconding only)so unclipping to untangle is quite helpful.