What's the quality of code produced by Mono? How does it compare with Microsoft's compiler? I'd like to see Mono C# and F# numbers compared against Microsoft's compilers. Will I get 90% of the performance?

There are games running on Mono (e.g. Unity C# scripts, Bastion was ported to Mono to run in Chrome, etc..). I'm sure the performance of Mono may depend on your specific application but many people have been using it without any issues.

Mono has been out for years, and I'm sure there have been great improvements. Does anyone have recent comparisons of it vs C# on Windows? I'm sure people must be curious.

the c# performance over mono is really different to the f# performance..while c# has a decent performance on mono, f# doesn't performance so well......

You can run F# on the old "stable" branch of Mono (2.10.x), but I'd highly recommend running Mono 3.0.x instead. The older version uses an older, simpler GC which works OK for C#, but which seems to have trouble with F# (which generates more G0 objects than C#). The new 'sgen' GC in Mono 3.0 is a huge improvement though, so you shouldn't see much (if any) performance difference between F# and C# apps.

Do you have any links with benchmarks? Very interesting.

Depends on what you're doing. Mono 3.0 has a stable llvm backend. For low level code it should run as fast as c modulo array bounds checks etc.

Some examples of why .NET is a Windows technology:

http://www.mono-project.com/Guidelines:Application_Portabili...

No. Those are examples of portability issues when your application depends on platform specific functionality:

Most code containing P/Invoke calls into native Windows Libraries (as opposed to P/Invokes done to your own C libraries) will need to be adapted to the equivalent call in Linux, or the code will have to be refactored to use a different call. <-- Means when you choose to directly link to Windows technology.

Registry <-- If you choose to use it. I haven't written any registry dependent code for the last ten years and don't even miss anything about it.

you should not assume the order of bytes <-- Not .Net's problem.

... the list goes on.

it's tied in the sense than the madurity over mono is a really long distance over the net one...I try use mono and f# in win xp..the answer was.."you can't...install w7 and vs2012"...that is annoying...the "mono community" are only a few guys compared to the .net support...so yes...it is really tied to .NET.....