We are about to develop a web app from scratch using ASP.Net, and would like it to be as platform-agnostic as possible. As far as I know, the only two options for this are IIS on windows, and Mono (via Apache) on Linux.
The app will be follow the MVC architecture, so with all of this in mind, how difficult is it to develop the application so that it meets these requirements? (I would think that ground-up platform-agnostic development would be easier than porting an existing app.)
If you are talking about ASP.NET MVC I am not sure that it is supported by MONO.
I am a big fan of ASP.NET, as it is what I do for a living, but I personally do not find that MONO is really a production ready, viable solution.
If you must be able to run under IIS or Apache you might consider different technologies.
Nope, it's not difficult at all. Most of the things work very well. The tricky part is configuring the server, not development. I've deployed several apps developed in Visual Studio on Apache/Mono/Ubuntu and they worked pretty well without any modifications.
If you do .NET 1.1, there won't be any problems, but if you do .NET 2.0 keep in mind MONO doesn't support .NET 2.0 100%, so you'll have to read up on the gotchas.
The mono project talks about this on their site. But in summary, they just don't support WebParts and a couple minor niche things that you probably won't run into.