I'm working on an application launcher so what I've seen might be different from what you'll see.
Probably. We use Qt for an application [1], and we didn't encounter any serious problems on Linux/X11. We never had to dig deeper than any of the Qt classes. Qt itself has some weak spots (e.g. if you have a table view in a tab with very many items, switching between tabs can become very slow). But the most serious problems we encountered on OS X, mostly because Qt doesn't naturally map to how OS X applications work (e.g. Document-based interfaces, OS X-specific features) and Qt on OS X seems to be less well-tested (e.g. between Qt 4.7 and 4.8 the default renderer was changed, but the new renderer had a bug, which broke painting in our application).
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I'm working on an application launcher so what I've seen might be different from what you'll see.
Probably. We use Qt for an application [1], and we didn't encounter any serious problems on Linux/X11. We never had to dig deeper than any of the Qt classes. Qt itself has some weak spots (e.g. if you have a table view in a tab with very many items, switching between tabs can become very slow). But the most serious problems we encountered on OS X, mostly because Qt doesn't naturally map to how OS X applications work (e.g. Document-based interfaces, OS X-specific features) and Qt on OS X seems to be less well-tested (e.g. between Qt 4.7 and 4.8 the default renderer was changed, but the new renderer had a bug, which broke painting in our application).
[1] http://rug-compling.github.com/dact/