The face can look wooden if you overdo it. I've certainly heard about people who go a little too far with it. Botox doesn't actually remove the wrinkles. It's just that if you can't frown, you won't be able to show off the creases in your forhead. If you can't squint, the crows feet won't be so obvious. The question is, how many facial expressions do you want to get rid of?
At least the effects don't last forever. So if you go too far, time will take care of it!