yep..I change from f# to scala and actually know many developers doing the same change...scala in first instance looks more verbose but actually it's much more powerfull (higher kinded types, scalaz, macros,etc) actually after accustom the syntax you find a clear and concise language (with ugly type annotations)
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.....
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.