I played with Qt for some time but I prefer managed environment of C#. I also keep reading about C# Mono framework working on Unix, iOS, and OS X. Can someone with first hand Mono experience share his/her findings?

I had experience with InstallShield, VS2005 Installer and NSIS. My preference is with NSIS. It works fine, more flexible, simpler and powerful. It is popular enough to get someone to answer your questions on various user forums rather quickly.