Technically, Symbian is still the market leader by a comfortable margin.
(The development options are fairly confusing though. For C/C++ development, the only Symbian dev avenue worth considering nowadays is "Nokia Qt SDK", which is surprisingly nice. Java seems to be essentially deprecated, but higher-level options like Python and JavaScript through Web Runtime are available.)
I agree that Qt is "surprisingly nice". Personally, I enjoy the iPhone UIKit framework, but the Qt SDK is almost as good (and in some areas better). I don't have much experience with the WRT, but in the N8 the demos I have seen are quite impressive performance-wise.
[disclaimer: I work for Nokia, take all I say (on this matter) with a grain of salt.]
(The development options are fairly confusing though. For C/C++ development, the only Symbian dev avenue worth considering nowadays is "Nokia Qt SDK", which is surprisingly nice. Java seems to be essentially deprecated, but higher-level options like Python and JavaScript through Web Runtime are available.)