It does something completely its own (and horrible/slow) on Windows (possibly one of the 6534 equally awful Java UI packages), so I can't imagine it does anything better with iOS.
Eclipse uses SWT, which actually piggybacks on native toolkits, though I don't know if it doesn't go through some ancient version of GTK in the process.
AWT/Swing based IntelliJ manages to be much, much faster in comparison.
