Only after setting up my girlfriend's and my own Lion user account to sync with iCloud did I discover that the address book still doesn't lend itself to sharing in the way that calendar does :-(
We currently use a single iTunes library on my user account for syncing both of our iPhones to a single address book, where all her contacts are in a folder called "girlfriend's contacts". This allows us to share our contacts but still (in a way) keep them separate.
What I'd like is for her to keep all of her contacts in her own, separate address book in her existing user account on my computer. We would then share our address books with one another (read-only or not).
Is there a work-around using iCloud or any other service? I guess we could continue syncing our contacts in the old way via my iTunes library (effectively mirroring our combined contacts in two separate iCloud accounts), but that's not very elegant...