You ara at it again. With C++0x still unpublished it could be argued that, in fact, C++ is more "modern" than C# (I assume that's the language chosen to write Tomboy). Also, grabage collection is hardly anything "modern". There are several "ancient" languages with automatic memory management (and reflection, generic programming and any other feature C# can claim, and some others it cannot).
The rest, only time will tell, but it will be interesting to keep a eye on both.