[akie]

If coding in Java is an option, I would highly recommend SWT (http://www.eclipse.org/swt/). It's the toolkit that was used to build Eclipse, and it has a very 'native' look & feel (click the link for examples).

Plus, Java itself is cross-platform. Might be just what you're looking for.

[safetytrick]

Java GUI's always seem just a little bit unresponsive, an irritating latency with every small move you make. This is my biggest complaint with eclipse and every other java app I've ever used.