If you use Opera Mini, be sure to update to the latest Opera Mini 4.1. And if you are using it on a Treo [operamini41, operaminiusage, operamini4], make sure you have the latest "silent update", opera-mini-4.1.11355-advanced-int.prc. Also check the IBM Java VM Prefs for optimal Opera performance:
[x] Use Double Buffering
[x] Use high resolution coordinates
Set Memory Maximum: 1Mb
Set Maximum Java Thread Stack Size; 32Kb
And if you aren't using Opera Mini, get it now!
The Opera Mini 4.1 update makes the already fast mobile browser even faster and more responsive. Connections are faster, page rendering is faster, and page scrolling is faster. And as I've found after testing tons of mobile browsers, outside of accurate-enough content, the only thing that really matters on a mobile browser is speed.