I have been playing around with php-gtk recently and in the past I have experimented with Java to make GUI 'hello world' apps.

However both these types of applications have had a bit of a clunky (almost childish) look and feel to them. I cannot deny that they are handy for making apps for in-house use (and I totally respect the amount of community effort that goes into these projects). But I would not necessarily be proud to sell it as a commercial application with a price tag of, say, £450 or £1,000.

If I wanted to make an application that had the look and feel of, say, Firefox for Windows, or Adobe xyz, what GUI/language should I use?

Is the 'professional sheen' or smart look and feel down to the designer or is it the case that, no matter how good a designer is, picking the right GUI framework is essential to get that look?