I have sold several sets and they have been good, solid reliable hubs for everyone I have put on them. I have a rear on my bike and I like it. The whole proprietary cog thing has never really concerned me. They are well made from stainless, wear very well, and are available now. I have a bunch of cogs coming for myself and some customers just to have a nice range and a few spares for the future. Stock up from the start and replace your chain regularly so you don't wear them out prematurely. As to the flip-flop option, they are also available with a freewheel thread so you can use a standard freewheel.