Strange, I found youtube playback to be done exceptionally well, the vids looked great and I think they loaded even faster than they do in Safari on my laptop... then again I never upgraded my iPad to 4.2 (or whatever it is) and thus didn't have multitasking etc..
Regardless, I expect the next one to be a workhorse. My only complaint about 1st gen is the speed at which it renders long webpages and forums... I like instant, but you have to scroll and then wait a fraction of a second. Not a big deal, but its not 100%.
I had the first ones out that were released. I agree with the webpage loading. I also didn't like the fact that I wasn't able to get a lot of software installed that I would normally want to use. The apps offered on the market that would substitute were pathetic. For that reason the adam looks pretty good to me right now. It's specs, loading and ability to handle multiple software running is really good.
Reading PDFs on the ipad even at 9" screen was bad. The margins settings were annoying you had to manually zoom in per page or set the margins per page. Hopefully these things get improved with new apps.