There used to be someone from Friendboy (FKA Rentboy.pro) who posted on this forum pretty aggressively trying to drum up business. The site must be gaining popularity judging from the number of listings, although there are serious limitations in functionality.
I just looked at J2G and agree with @Fyton that it's slick with lots of features. Seems to share some elements with the RM site, just using different art design. There are guys on there not found on RM, and at first glance more masseurs, at least for my area. Maybe it seems less hardcore and will attract providers who wouldn't normally advertise on RM.