I've never tried one, but I'm curious nonetheless.
I've used wood body jewelry before (plugs for my stretched ears), and the general rule of care is to not get them wet because the wood can swell and splinter/crack as a result. The plugs aren't sealed though, and it's suggested that you oil them with jojoba periodically to keep them in good shape.
I haven't looked into the suggested care for wood toys, but if they're sealed heavily with no chance of the sealant wearing off, I would definitely give them a shot.
What I'd REALLY love to see are bamboo toys. I wonder if bamboo is good enough to be made into toys. The sustainability would make all the difference for me.