Nope. Never done anything more than the "hello world" XPage. I did see enough of it to know I wouldn't like working in that environment though. Seems an awfully messy way of working to me.
But it's not about what's possible with XPages. It's about whether there's any demand for it from paying customers.
You have to remember that my (fundamentally flawed) business model is to be so well known in a particular field that works comes to me. I don't have a product to sell and don't go out selling solutions based on any one technology. I just wait for people to ask me to create a solution on a technology they (most the time) specify.
Whether I can ever reproduce this business model outside of Domino remains to be seen. I'm not overly optimistic that it won't involve a return to office-based contracting and living in B&Bs. I'm hoping not.