>>1
There are three separate problems here:
1. Ugly interface. Solution: get a skin that looks more GTKish. And Opera's file dialogs might look like shit and have bugs, but they are more usable than the GTK dialogs.
2. Bitmapped fonts. Go to opera:config, find the 'Enable Core X Fonts', setting, and disable it.
3. Fucked up smoothing/hinting. Known problem caused by Qt being a piece of shit. You could try this:
http://my.opera.com/community/forums/topic.dml?id=230415&t=1209513259&page=1#comment2535346
(I haven't yet because it requires an X restart).