For someone who’s been happily programming in C# for quite some time now and planning to learn a new language I find the Python community more closely knit than many others.  
Personally dynamic typing puts me off, but I am fascinated by the way the Python community rallies around it. There are a lot of other things I expect I would miss in Python (LINQ, expression trees, etc.)  
What are the good things about Python that developers love? Stuff that’ll excite me more than C#.
Your question is kind of like a plumber asking why carpenters are always going on and on about hammers.  After all the plumber doesn't have a hammer and has never missed it.  Python (even IronPython) and C# target different types of developers and different types of programs.  I am very comfortable in Python and enjoy the freedom to focus on the business rules without being distracted by the syntax requirements of the language.  On the other hand I have written some fairly substantial code in C# and would be very concerned about the lack of type safety had I taken on the same task in Python.  This is not to say that Python is a "toy" language.  You can (and people have) write a complete medium or large application in Python.  You have the freedom of dynamic typing, but you also have the responsibility to keep it all straight (frameworks help here).  Similarly you can write a small application in C#, but you will bring along some overhead you do not likely need.
So if the problem is a nail use a hammer, if the problem is a screw use a screw driver.  In other words spend some time to learn Python, get to know it's streangths (text processing, quick coding cycles, simple clean code, etc) and then when you are looking at tackling a new problem ask whether you would be better off in Python or C#.  One thing is certain.  So long as C# is the only programming language you know, it is the only one you will ever use.
Pat O
What Python features will excite the interest of a C# developer?