Has anyone used them? Which one(s)?

I'm wanting the Tease pretty badly. But some of the reviews mention the vibrations being weak? When I checked out other Little Secrets, the Whisper is apparently much stronger; do they have different bullets or something, or is it just the silicone sleeve that dulls the vibrations? I'm assuming the latter, which is unfortunate because the Whisper is honestly my least favorite from this line. I LOVE the design of the Tease. Do want.

EDIT: Also, for those of you who found the vibrations lacking, has anyone tried putting the sleeves over other, stronger bullets? I may consider trying this if the one I purchase isn't quite strong enough.