My U3 are like my cats, they need a bit of attention but most of the time they're fine.
I don't think that the occasionnal zombie is a problem (well, unless it's a cat then it'll eat you while you sleep)

How many do you have? When I had 3 on windows i caused multiple times a day of attention.
The worst ones were if I was not around it sit there zombied, and no hashing. CrazyGuy's R1 really is great at fixing zombies.