It's nice and probably uses way less system resources, but it definitely isn't as "polished" as the Flash version was. Not sure if that's a limitation of the HTML5/JS/CSS combo or if they just need to work on it more. It's mostly just little things, like missing visual fade transitions or a UI that doesn't look like it's been repeatedly bleached. But they add up to a noticeable difference, I think--the HTML5 app just isn't as vibrant.
That being said, I always thought their Flash app was amazingly slick and polished, so it's a tough act to follow I suppose.
EDIT: Plus if they are going to go this far with HTML5 it'd be awesome if they could cut the Flash cord entirely. Not sure if that's technically possible though.
I know the Grooveshark fans who are Linux users will appreciate the increased stability as well.
On Ubuntu 10.04 x64 Flash is pretty stable for me, except when I've got 40 Firefox tabs open (yes I'm seeing a therapist about that) and then try to run some Flash app that's more complex than a mere Youtube video. No more popping htop to manually kill nspluginwrapper that's in some kind of infinite loop ftw.
I'm not really sure this is HTML5. Looking at the source code, you don't see many of the hallmarks of HTML5. There HTML tag itself is distinctly XHTML 1.0 Strict, and the lack of any true HTML5 tags (e.g. SECTION, NAV) imply to me a hybrid -- a platypus, if you will. They do, interestingly, use HTML5 data tags.
That being said, I always thought their Flash app was amazingly slick and polished, so it's a tough act to follow I suppose.
EDIT: Plus if they are going to go this far with HTML5 it'd be awesome if they could cut the Flash cord entirely. Not sure if that's technically possible though.