Sonic cleansers for face?

Has anyone tried one of the sonic cleansers for the face? QVC were advertising one yesterday.

They are round and flattish with tiny raised "teeth" on each side. I think they are battery powered and when you've covered your face and neck with your normal cleanser you pass the sonic cleanser over your face in circles to clean off all the make up/dirt from the pores more effectively than just wiping with cotton wool or a hot cloth.

I have large pores in places and I'm wondering if a sonic cleanser would do a better deep-cleanse.

I'm not sure where the dirt is collected and how you clean them after each use. Perhaps you can run them under a hot tap or maybe they come with a little brush to clear out the dirt that has been collected.

A review saying which one you have and if they do a good job would be welcome.