I'd be curious as to what exactly you mean by "success stories". If you mean something along the lines of "is it easy to develop, has a robust environment, and doesn't present any hard problems" then I think there's a lot of companies out there. If you mean something like "will it help your company produce something people want"? Then you're asking the wrong question. Tech <i>very rarely</i> determines product-market fit, at least not to the degree that we developers think it does.<p>I've been using F#/Mono for my small apps for some time now. For an example, my personal news aggregation site, <a href="http://newspaper23.com" rel="nofollow">http://newspaper23.com</a>, is running all the time, going out and finding headlines and presenting them to me in plain text. Been meaning to add a text stripper to the mix so I don't have to see any ads or participate in any sticky website nonsense at all; just haven't had time to code it yet.<p>The nice thing for me, especially for this app, is that I can use F# in a purely functional manner to create little unix-like programs that do a little bit of work at a time. Then I string them together with chron and, instead of the old client-server web model, I have something more resembling a data <i>pipeline</i>. I can monitor flow across the pipeline, distribute parts of it to other machines (scale out) if necessary, and so on. All without having to re-code anything. The entire thing serves up a static web page, which can also be tweaked: served in-place, over a CDN, emailed to a user, etc. Did I mention the "no recoding" part?<p>As a former .NET guy, I'm happy enough with F#/mono that I can't imagine going back to full-bore .NET no matter what the problem domain. The toolset is way too heavy, the culture is awash in folks marketing to developers instead of helping them build stuff people want, and so on. It was a great ride, but F#/mono is where I get off.<p>Having said that, I still use the VS IDE to develop, since you can develop in windows and then FTP the code over. That's pretty cool. I've tried and used MonoDevelop. I guess it's okay. I've also done a bit with just straight-out command-line compiling. After all, it's not like you need a huge codebase full of hundreds of files. Or if you do, you're doing something wrong :) An 8 or 10-file F# program is a monster -- and probably means you're trying to do too much at once.