So I'm aware of the big ammount of general-purpose scripting languages like Ruby, Python, Perl, maybe even PHP, etc. that actually claim being usable for creating desktop applications too.
I think my question can be answered clearly

Are there actually companies using a special scripting language only to create their applications?
Are there any real advantages on creating a product in a language like Python only?
I'm not talking about the viability of those languages for web-development!
Should I stick with C(++) for desktop apps?

best regards,
lamas
I would recommend you not try to look for a language that is best for GUI apps but instead look for the language that you like the most and then use that to write your app.
Ruby, Python, Perl all have GUI tool kits available to them. Most of them have access to the same often used tool kits like TK, GTK, and Wx. The look and feel of a an app will be dependent more on the GUI tool kit than on the language, and performance wise your likely to see more impact for how you write your app than language choice.
If your comfortable with C++ then you should also look at C# or Java as options. While not scripting languages they have many of the same benefits like memory management and more sane string implementations.
"Real" and non-embedded use of Ruby, Python and their friends