For the two of you out there who use Opera, I just gave it a cursory test :)
It seems to work fine, the only weird thing is that the Google Maps markers seem to appear a little to the right and down of where you think you are clicking. Once you realise this is happening it’s fairly easy to account for this when you click. Also, of course, as you can drag markers, you can always drop them roughly and then drag them to the exact position (this seems to work fine).