Actually, I do have one. It's hard to tell how much they help, but I do think they're great. They're also quiet, so I can do them in my room before I go to sleep and not bother anyone.
Yes, they can leave you feeling bruised, but that's why it's really important to start slow and work your way up. I would start with about 3 minutes and work your way up. I wouldn't go much beyond 8 minutes, twice a day, but I know some people do. I think everything should be in moderation.
I hope you enjoy it! It IS a great gift!
First goal: under 180:
Second goal: 175 or below:
Third goal: 168 (no longer overweight):
Fourth goal: 160 or below:
Final goal: 145-155 (not sure if this will ever happen):