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Oxygen looks quite nice on native apps but sometimes ugly with non-native apps. I'm not a real windows 7 fan, but aero looks good, maybe because on dark line between window content and window frame.
I might have been tired of all of this oxygen stuff, it's sometimes too hard to look at. Someone should do something about that, i'm switching between kubuntu and ubuntu because ubuntu uses warm colors, ui is simple.
I need to complain about Air plasma theme. Beautiful, when used with default placement and height. When I place it to the top of the screen and change it's height small, then it's just ugly. Tray icons are 'off', window decorations doesn't integrate well.
I could continue but i don't. My idea is this: someone should design and rethink KDE. Features are good and I love KDE but after few hours of usage I'm frustrated with it and switch back to unity.

Use a different theme. This isn't an idea, this is a personal aesthetic preference.

If you are experiencing alignment issues, then that is a bug and should be reported to bugs.kde.org.
If you are experiencing a lack of design thought when the panel is placed above at certain pixels rather than the default, then contact the oxygen team (see: Nuno Pinheiro).