I actually made tests a while ago to show precisely those two things, namely flooring and drawImage, are 10x as slow on Opera. First let me note that on averag

I actually made tests a while ago to show precisely those two things, namely flooring and drawImage, are 10x as slow on Opera. First let me note that on average using Math.floor(x) results in slower performance than using x | 0. I'd recommend using the latter way instead. And even then Opera is an order of magnitude slower at flooring numbers compared to FF5, IE9 and Chrome 14: http://jsperf.com/bit-thingies http://jsperf.com/bit-thingies Opera's drawImage is also an order of magnitude slower than Chrome 14, IE9 and FF5. Note that in this link the FF8Beta, Ipad, and the first two Chrome versions were ran by someone else's machine, so those results can't be compared with the other numbers. http://jsperf.com/render-vs-prerender http://jsperf.com/render-vs-prerender If you don't believe them, of course, I urge you to run them for yourself.