I like both Haskell and F# so perhaps i can give some reasonable counter-arguments.
1) F# will be integrated in Visual Studio 2010. Large commercial companies like banks use F#. It is very unlikely that Microsoft will drop it.
2) Actually the F# team responds very quickly to bug reports. Just send your report to fsbugs@microsoft.com
3) F# is not yet open source, but the source code is available. They have promised to eventually open source it like Microsoft has done with IronPython and IronRuby.
4) Visual Studio Express editions are free. It would be nice if MonoDevelop had a good add-on for F#.
5) No arguing with that. Haskell can be very elegant and has a very good community.
6) I could argue that F# is more cross-platform than Haskell. Despite Simon Marlow's amazing work Haskell's Windows support is lacking compared to Linux. There are no current plans for GHC to support 64-bit on Windows and several Haskell packages use low-level C libraries which can be less reliable on Windows or difficult to compile whereas the .NET framework and Mono function as a common abstraction layer between Windows and Unix.