I know there's a lot to like about it; I loved (in my brief exposure) the cards metaphor, and I imagine that development could be quite nice, but have they solved the issues he refers to?
[disclaimer: I have had a brief play with a Pre, but you can't get them in Australia. I would have considered getting one].
That being said, the system doesn't feel as 'instant' as the iPhone or a fast Android phone. However, you can often get things done faster than competing platforms because the workflow is so streamlined.
Moving to a 1Ghz processor like the Snapdragon would probably bring responsiveness up to parity with other systems.
WebOS, on the other hand, displays notifications peripherally and in parallel, it consolidates and organizes them by application, and even has two levels of hierarchy for initial and persistent alerts. It's an order of magnitude more powerful, yet elegant enough that it would be at home on any Apple device.
Not the case, in my experience. Generally, they pop up one after the other, right when you're about to tap on one, and then you have to either dismiss each one separately, or open the application responsible for the most recent one and hope for the best.
Notifications on iPhoneOS are the single worst user experience, and I can't understand why Apple hasn't yet fixed this ridiculous and annoying problem once and for all.