C API is the big one. Unless your language is officially supported by Qt (meaning C++ or Python) you're basically screwed.
Secondly would be the license, while they're both LGPL these days, that wasn't always the case, and the current Qt company is highly hostile to open source.
Secondly would be the license, while they're both LGPL these days, that wasn't always the case, and the current Qt company is highly hostile to open source.