Hi Tar,
Since I have a serious Java fixation, and get scraps from a nearby restaurant, my worms go through a lot of coffee grounds. I haven't tried it as a primary bedding, but our good vermicomposting friend at Red Worm Composting has with mixed results:
http://www.redwormcomposting.com/worm-c ... conundrum/I think if you pre-composted the coffee past the heat stage with some browns (fall leaves, newspaper, cardboard, straw, etc) it would be ok to use as a bedding. Maybe put the coffee grounds on one side and half done compost on the other--the worms would have somewhere to go if they didn't like it at first. Also, you might want to add ground up eggshells to reduce acidity of the coffee. If it is a new bin, I would inoculate it with a little compost or Vermicompost form another bin and let it sit for a week to buildup a microbe colony before introducing the worms.
A preferred PH seems to be about 6.5-7, but I've read that worms are fairly adaptable between 4-9. Since all the inexpensive PH meters I have looked into got raging horrible reviews, I tend to "feel" my way with my worms and use common sense (don't overload on acid, or add some calcium source to reduce it, only put acidic stuff in a corner of a bin so worms can go elsewhere, etc.).
I would love to hear more about your bin when you get it up and running.