"Users have all the options in the world and are ready to move on to somebody else's site if they face a tiniest obstacle on yours. It's getting harder to sign them up."

This is true but on that very subject I can't help thinking that the splash page is the thing that will interest people or drive them away. I think Dolphin's needs a fair bit of work on it in my opinion. Other platforms, especially OSSN have an awesome page, only problem inside OSSN is it's identical to Facebook & see more I don't want that. Dolphin is a lot more flexible but the splash page needs some work doing on it as a default.

Aside from that, great job on the login, it looks a whole lot better. Simplicity is best :)