JomSocial looks very solid and impressive on the demo site.

My company bought a copy for implementation. Unfortunately, we have some large projects to complete before I can start tinkering with JomSocial. I'm looking forward to customizing it for our site.

I think Community Builder is going to have a tough time competing unless they really work on their UI and design. I have yet to see a CB site that's as smooth as the JomSocial demo. I know CB has a lot of fans and has been around for a while, but I don't think it holds up design-wise to what's expected from current Social Networking sites.

In any case, JomSocial looks to be a great addition to Joomla's commerical component library.