I think you shouldn't over-think the question. If you already know C# but are new to Ruby/Django/PHP, it's probably better to go with ASP.NET. I personally go with ASP.NET for the intellisense and refactoring support of Visual Studio. The main drawbacks for me are that deployment is more difficult and expensive than other frameworks.
For kicks, I deployed the same app on Ubuntu 10.04 and Windows 2008 R2 micro instances on AWS. I chose the plain Windows instance - with no software ( ie, IIS & .NET) pre installed. No database is used in this app.
I had the mono/Ubuntu version up and running in about 30 minutes. The longest part of the install was that I chose to use Mono 2.6.7 which isn't officially supported, so you need to do some work to install it. The app was deployed using FastCGI and Nginx.
It took about 90 minutes to get the Windows 2008 version running. Most of which time was spent waiting for the instance to start and waiting for the bloody Platform Installer (worst app ever!) to do whatever it does.
The moral of this story: the Windows micro instances are unusable. But to scale vertically, use Windows. To scale horizontally, or if you are cheap||frugal, give mono/Ubuntu a shot. Can't wait to see what moving to LLVM is going to do to mono's performance.
When you work for a company that already runs on MS infrastructure.
Jeff Atwood of StackOverflow also claims that they have much lower server requirements because C# inherently runs faster than non-compiled languages such as ruby/python/php, but of course there is some debate about whether that balances out the higher cost of IIS/SQLServer licenses.
I'm not an expert in ASP.NET MVC and I'm not a hater either -- but it doesn't seem to offer anything that Rails doesn't (other than aforementioned runs-on-MS-stack and compiled language).
Would love to hear other opinions from people with more .Net MVC experience, though.
That's a pretty fair question. In my opinion, the only reason to go with ASP.NET anything is if you already know C# (or any other .Net language).
Otherwise, Rails, Django, Flask, Cake, etc are going to be significantly easier to get up to speed with, have better communities, have less murky IP situations and are generally going to be less expensive to develop for and to hire developers for.
There are advantages to the CLR world - Tooling is top notch (Mono's tools are lacking right now but seem to be improving quickly), there is a reasonable amount of documentation, even though some of it is of questionable quality. C# performs well, both on Mono and .Net. There are many libraries available (although the quality of the libraries can sometimes be lacking). Many of the higher quality libraries are closed-source commercial libraries. Some of the worst ones are also closed-source commercial packages, so it pays to do research prior to purchasing anything.
The community has been warming to open source - in my opinion this is largely due to the efforts of Miguel de Icaza and everyone working on the Mono Project. (As an aside, if you don't like asp but you do like C#, you should consider checking out and contributing to Manos de Mono, a Mono based web framework which is still in its infancy - https://github.com/jacksonh/manos .)
Microsoft is, and always will be a for-profit company that makes money from selling its software. It has a vested interest in creating platform lock-in, but developers don't have to stick to the Microsoft way of doing things if they choose not to, thanks to the strength of Mono today. Either way, Microsoft is pretty up-front about what the cost of doing business is with them; and they have proven to be pretty consistent with their pricing.
Politics and profits aside, C# is an enjoyable language to use. I haven't spent time with F# yet, but I understand it's quite enjoyable as well. The C# team has done an excellent job of paying attention to programming trends and adopting techniques from other languages. The transition from 1.1 to 2.0 was kind of clunky, but since then they've shown a great deal of good taste in what they've implemented as well as how it's been implemented. Of course, the downside is that C# is a large and complex language. I think the most recent "C# in Nutshell" book is well over a thousand pages.
I have production code deployed in Python, PHP and Clojure, but I'm currently migrating back to .Net for my personal projects. C# developers get an excellent cross-platform deployment story thanks to Mono (MonoTouch, MonoDroid, MonoMac). Honestly, I think Mono runs on pretty much everything from PC, Mac & Linux to WP7, iPhone and Android; as well as game consoles, embedded hardware, etc.
Additionally, many of the new to .Net technologies coming out of Microsoft right now such as F#, C# 5's async framework, MVC3 and Entity Framework 4 are very compelling. Microsoft is kind of a dorky company, but in my opinion they are producing pretty good software right now.
