Here are my observations so far from 15 minutes worth of use...
Pros:
Its fast
Unlimited tabs? (seemingly)
Tabs don't reload when you quit, they even stay in Airplane mode
Nice bookmarking
Customizable settings (like full screen mode) are neat, along with image quality
Pressing back / forward buttons results in nearly instantaneous navigation - cached?
Cons:
Zooming sucks - only two levels, can only be zoomed in on landscape? Sometimes zoom gets stuck in portrait
Comes with titlebar by default - option to make fullscreen - just want option to get rid of title bar
Text selection is inferior
Have to double tap on items in history drop down
Feels "loose" compared to Safari - hard to describe
Tab browsing is difficult with too many open
Bottom line:
If Opera can get their zooming and scrolling under control, this thing might make it to my first page on my home screen.
Until then, the only way it will get there is my utilities folder come summer! I can only see myself using this when the internet is especially slow--like out in the country or at the AT&T black hole that is my mother-in-law's house. This browser is very fast, and fairly customizable with lots of tabs and it stores them before quitting. I believe this app has a lot of potential, and quite frankly would like to see Apple implement some of these features in Safari (ESPECIALLY SAVING TABS ON IPAD WITH ITS 256MB RAM!!) Though I can always hope for 4.0 and saving states for fast app switching. Seems to be the same basic idea as this, though this optimizes things a bit resulting in a smaller page size.
It is good to see Apple approve something like this, and hopefully other developers like Mozilla can now find a way to produce a similar app that "beats the executable code system" by rendering outside the app. This opens the door to further possibilities, if implemented properly. Kudos to Opera for innovating a way around. This goes to show that Apple only locked down browsers in the app store for security purposes. Hopefully they will eventually be able to completely sandbox entire apps from the OS so we can get native Firefox! Imagine the multitouch plugin goodness.
Edit: What the hell is with this intrusive ad banner that just flew across my page and covered up the center of it? I'm writing this from FireFox on a Mac. Is MacRumors finally implementing all the corny, invasive ads seen on equally corny sites? I thought this place was classy. Maybe it was just a glitch, but I hated that survey popup.