The truth is that I do not know that much about C# save for what I have read in forums and articles in places such as GameDev.net. For some reason nothing about it has piqued my interest me enough to look at it further. This is not a good enough explanation, so I did a little bit of digging in C# tutorials and resources on the 'net to try and figure out why C# just does not excite me.
In short, I think there are three main reasons why I do not think I should use C#, at least not yet. These reasons may be irrational or based on faulty information - I really do not know enough about the language to make an accurate judgement. But they are what I currently feel, and at least by posting them here I know that more experienced programmers can correct any misjudgements that I have.
C# is too much like Java
My first big turn-off is that C# feels far too much like Java. If I have my knowledge right this is intentional: C# is Microsoft's take on Java with a combination of some elements from C++. However I have never liked Java that much, so this does not endear C# to me from the beginning.
My dislike of Java probably is pretty irrational, based on both my history dabbling with it and my preferred programming style . I first learnt the language back in the late nineties as an undergraduate. We would use Java as graphics front ends to applications like our large fourth year grand software engineering project. Our lab had all the outdated Sun SPARC terminals, where you would be hoping to get the ones where the monitors were in quality monochrome. Java 1.2 in those days had a reputation to be slow, and that certainly was the case on our hardware. You would spend up towards a minute just for the GUI screens to show up. I never got too deeply into Java in those days, preferring to stick to C.
Then there were my days as a tutor. Amongst the classes I took was one on Human-Computer Interaction, spending a bunch of classes arguing the merits of interface design with disinterested students (computer science students don't seem to like having to deal with tutorials that involve class discussion). Halfway through, it was sprung on me that I also had to take labs in Java. At that time, the only skills I could remember were essentially the bits that overlap with C++. It wasn't pleasant.
These are purely anecdotal and are unfair to current Java, I concede. I am sure that the latest version of Java (it's up to 1.6, I think) on current hardware is nowhere near as painful as it was nearly a decade ago. However it has left me with a slightly negative opinion of the language.
Other slightly more relevant complaints I have about Java: it is increasingly being used as an introductory language for students. Okay, this might also be unfair to Java, as my complaint is more directed towards how it is taught than a limitation of the language itself. Every Java tutorial I have seen has jumped into fancy library calls and GUI elements before I think it is warranted. To show what I mean, here's the first link I got Googling for "introduction to Java", the chapter listing for Introduction to Programming using Java. Note how the chapter for GUI programming comes before the ones for arrays. I think focusing too much on pretty GUIs that early is counter-productive. Early programming should focus more on learning the basics of breaking down problems into programmable elements, not on producing applications! I have seen too many undergraduate programmers who work on the cut-and-paste method; they are good at finding code that solves their task exactly, but they do not understand how it works. Personally, I would recommend something academic and functional like Haskell or some other ML language as a warm up before moving into an industrial language.
My other gripe is one which is slightly more relevant to C# (there's a lot about Java here for a C# post!). I don't like how rigidly object-oriented Java is, and by extension the same applies to C#. This might be a hang-up from my C days, but I don't like forcing everything into objects when it feels more natural not to. I suppose they can be considered another form of namespaces, but even then it seems a bit over the top.
That might have been a bit more ranting towards Java that was necessary. Most of those points are about my own personal tastes and do not apply to the Java and related languages in general. In truth, I don't actually dislike Java, much like I don't dislike any programming language (well, except maybe Perl - wait, better not get side-tracked again). Java just has not gelled with me the times I have tried it; its form and function does not appeal to me as a programmer. Since C# looks very similar at a glance, this opinion has rubbed off on it.
C# is too closely tied with Microsoft
A rather contentious title, to be sure. Don't worry; this won't involve terms like the "evil empire" or misspellings involving dollar signs.
These days I develop on an iMac. I would like to write cross-platform code for both Mac OS X and Windows (at the least. Possibly Linux as well). So the choice of language for production code needs to be painless for developing under Mac OS X as well as deployment for multiple OSes.
While I do know about Mono and the standardisation of the C# standard, I cannot avoid that, much like how Objective C is associated with Mac OS development, whenever C# is mentioned it almost always is treated as being entwined with .NET for Windows. It is assumed that you are compiling with Visual C# under Visual Studio, aiming for Windows or possibly the Xbox 360. There is also the issue that the ties to .NET mean there is an extra condition placed on anyone who wishes to use my applications, which is a complication that can be avoided with other languages.
Consequently, this makes me somewhat wary how painless cross-platform C# will be in practice. It has been annoying enough with C++ to have everyone assume you are using Visual C++ for pre-compiled libraries. I suspect that Mono will always be one step behind Microsoft's version of C#. And there's always the risk that, much like Sun did with Java, Microsoft might get overly protective of improvements to their language.
Other languages will do the job
This reason is straight-forward. The big reason I have against devoting a lot of time to trialling C# is that I feel other languages will work admirably. If it ain't broke, don't fix it. Given I don't have anyone placing restrictions on my language choice and I've got reservations against C#, I don't see any reason to pick it up. As far as I can tell, Python with C extensions should fix the development problems that I have had with C++, and work better with my programming style to boot.
Trimming out some of the Java rambling, that's my reasoning in a nutshell. The third reason is the most important one; I think I will enjoy developing in Python, Lua and C more than C#. When it comes down to it that's a very important reason to choose a language.
For any C# fans out there, please correct any faults in my reasoning. I'm not exactly "well versed" in the good points of C# and can be convinced by a strong enough argument. As it stands, I'll put my time into learning more Python, trialling Lua and revising C.