I have developed for Windows since Windows 3.0. Starting with MSVC 5.0 Visual C++ I have used all Developer Studio's.
One and a half year ago I researched our options for a X-platform basis for our software clients.
I looked at Mono for 2 hours before discarding it.
I finally chose Java SE, and it took me very little time to get used to the fabulous NetBeans IDE (looked at Eclipse too, but NetBeans takes much more care of things that aren't very obvious to Java newbies)
I am now porting our MSVC/MFC C++ codebase to GCC with the C++ standard lib and the impressive Boost library.
I had to refresh my C++ skills, regarding templates mainly, but it was well worth the effort.
After a lot of evaluations I decided to opt for CodeBlocks as my IDE. It's not comparable to Visual Studio, but certainly good enough!
So I'd recommend standard C++ for software that has to be fast (our software manipulates 1 bit TIFF G4 compressed files, quite CPU intensive), and Java for the rest.
You aren't working directly with Linux with any of these suggestions, but it will run very well on Linux, as on most other OSes,