Is using HTML as a UI for a desktop application sane at all?

[Turk]

I have a project in mind. One of the things I'd like to support though is using either Mono or .Net. This causes a problem with the UI. Winforms works on both(for the most part), but it's a fairly archaic and I'd rather not use it if I don't have to. GTK# works on both, but I'd rather not have to bundle it for Windows, and it can produce applications that don't really look native on Windows. (also I'd have to learn it)My application would for the most part would be very simple as far as UI goes. I considered making it a web application, but it would require users uploading files commonly, which can be a big pain point for users of sub-optimal Internet connections. So, for portability and ease of development, HTML as the UI for a desktop application would probably be the best. I've seen this done a some with people embedding a web browser control into their application. Because I'm aiming for mono compatibility though, this won't work for me. I'd have to point the user's browser to 127.0.0.1TL;DR:How common are desktop applications that use a web browser as their user interface? What are some of the big problems with doing it like that? What are the pros and cons?