As soon as I see "available on all major operating systems" I groan, because of course it seems to be a Java app. The user experience for Cocoa apps on OS X blows away that of a Java app. The reason Sequel Pro is great is because it feels like a first-rate Mac app and seamlessly fits in with everything else.
You can make a Java app feel almost native on OS X, like with Cyberduck, but it is really, really hard and you have to prioritize that target in your design. Then what happens, as seen with Cyberduck, is the Mac version coming out pretty good and the Windows version feeling a little "off."
I share some of your sentiments about x-plat Java UIs, but DbVisualizer does an admirable job. I now use on Windows for SQL Server for most tasks even when the native GUI is available. Its worth a look.
