ok, i'm a long time reader of cp but a first time poster. this is a post i feel strongly enough about to 'come out of the shadows' so to speak. i started using f# a long time ago, and did a tonne of development with it in the beginning. i think the major benefit of learning fsharp, and particularly the functional programming style (the value of immutability, etc) was that i began to think the same way in c#. it gave me a much better appreciation of performant code, and particularly functional linq. a few things i liked: the functional programming style, while still being able to code imperatively if you wish. the full access to the .net framework, with interoperability from c# the pipe |> forward operator the fsharp interactive (fsi.exe). for me, this has been largely surpassed by code snippets in linqpad (but i yearn for a csi.exe) including it's integration with visual studio generics (wait, they're c# you say? ...c# generics wouldn't have been the same without don syme and his team) decent support for mono. i got a lot of the great functions of f# 'out of the box' at a time when mono's framework was a generation behind .net 3.5. incidentally, if you need to target .net 2.0 for any reason, you'll get a lot of the linq-like goodness you're missing out on via f# and much, much more... if you haven't tried f#, go and get it now, try out a few of the code samples. if you have time, read robert pickering's beginning f# and don syme's expert f#. your c# will thank you for it. solutionevangelist ps: incidentally i was once in a chat with phil haack, etc, and asked the group how many people used f#. phil's estimate was zero. one person had a member at their company who'd used it for a production project. i'm somewhat disappointed at the lack of interest in f# by c#/vb.net developers when they *should* be interested. it adds a very valuable facet to the .net framework which is far more important than the likes of ironpython, etc. i am very encouraged by microsoft making it a first-class .net language with full support in their ide's, etc. i think it has a great future outside being a 'research' language (i know of a lot of financial traders doing amazing things with it in production). .net may also get the benefit of a lot of sharp people who've expressed important things (algorithms) in OCaml and we don't need to wait around for the same thing to be done in C#.