Canadian musicians Ian Tamblyn and Washboard Hank both play these guitars at times. Ian often brings two on stage with him, one in Nashville tuning and the other in an alternate tuning. Hank uses his when the Martin's in the shop.
Jimmy Bowskill also plays one sometimes.
John Sebastion played a Harmony Sovereign in the Woodstock movie.
I used to see them for about $350, but they seem to have gone up to near $600 these days - still a good deal.