Bit of a cross-post from my comment on the iPad forum but my initial impressions:
Hellishly fast!
Unfortunately it's got a few things to sort out before I'll be happy with it, on the iPhone at least:
* The default zoom/resolution on an iPhone is too large, so you can't read the text
* It seems to switch randomly between defaulting to 1:1 style zoom level and the entire page
* There's no proper zooming, there's a pinch gesture but it just switches between 1:1 and full
* Auto-correct doesn't work (it's surprising how much I used it)
I've always quite liked the Opera browser on the desktop and I think it shows a lot of promise but it's got some fixing to be done before I'll be using the iPhone version long term. It'll be interesting to see people's findings on the iPad one.
Definitely looking forward to 1.1, like I say it's blazingly fast and I'm sure once they've worked the kinks out it'll be awesome.