Invite help...

Has anyone used a calligrapher for their invites and would you recommend them?

My invitations were supposed to be in last week and I just found out that they won't be ready for another two weeks and I have to get them out the beginning of August.... My rsvp date was Sept 6. Is three weeks enough time to ask for responses? I wanted to leave a few weeks to track people down and send out the B list if necessary...