Tweetro, of course. I expected the swipe to be interpreted as a back to last app gesture, and that it was. Then I waited for a second or so. I swiped in from the left edge once more. Although not as confident as last time, I still expected to be switched to Mail, as an IE to Tweetro back to IE swiping sequence didn't make sense.
I was wrong. IE was swiped back in. I needed to find out why and see if there's some underlying logic that determined this. I would have been disappointed if there wasn't. Fortunately, it became quickly apparent what the rationale was. And I wasn't disappointed.
See, on Windows 8, the app that's swiped in from the left edge depends on when you last did a left swipe to switch apps. If like in my example you wait a second or more, you're returned to the previous app. The time delay results in an assumption made that you're continually switching between two specific apps. For example, you're writing an email but consulting a website/document/etc. as you write it. However, if you do a swipe within a second or so of the last, the switched to app is not the one you were on previously, but the next in the queue. The assumption here is because of the minimal time interval between swipes, your intention is to swipe through your running apps rather than jumping back to the last app.
Confused? Watch this video (apologies for the poor production values).
This is pretty great. It makes multitasking even without snap frictionless; you can switch between two apps seamlessly without any interruptions. This is a stellar feature on Windows RT that demonstrates a commendable attention to detail. It's one of those things you may not consciously notice, and that would explain why I've not come across anyone heaping praise on it.
It's little big details like this that make the Surface RT an attractive alternative to the iPad. There are many points that the iPad beats the Surface on, but multitasking is not one of them. And multitasking is a big deal. It's no small win. And that's why Microsoft should really be making a bigger effort to emphasise the practicalities this win brings to the user.