I have been working closely with Jamroom over the last few weeks to move my site, PaintMyPhoto, from Ning to Jamroom. It has been a huge task, with 26,000 members and 100,000+ high resolution images to move. We elected to use Jamroom's hosting service (which is working very well for us).
In a past life I worked with many software companies, but I have to say that Jamroom hold the trophy for excellent service. Everyone at Jamroom has been so helpful, we couldn't have asked for better service.
It is the case that you do need to spend a little time familiarising yourself with how the product works, but it really is worth the effort. There is so much potential available.
We are so pleased to have chosen to move to Jamroom and look forward to continuing to develop and improve the site using this great product.