I definitely want to try using a Writeboard for the very next technical paper I co-author with someone I can't pair-write with in person! and I'll be experimenting to see how it works with their BackPack companion product.
NB - I discovered BackPack and subsequently Writeboard as an indirect result of learning the sad news about the death of Brian Lyons of Number Six Software, who I'd met several years ago when he delivered some Rational training to one of the business units I was coaching, and we subsequently corresponded with several times. My heart goes out to his home and work families on this huge loss.