Had my first session last Friday and I have to say I really enjoyed it - even if I couldn't roll over a 10 to save my life (I think I only rolled over 10 three times - my dice hated me that day).
We had a good RP experience in the town our DM started us out in, then went on to have three combats interspersed with two skill challenges, and all done in less than three hours.
Combat was fast and smooth with the longest waits being for someone to decide which power they wanted to use.
Skill challenges were fun in that the DM provided a real sense of danger for failure. We were sneaking through a marsh to a goblin camp and with my horrible rolling I almost blew our cover.
I liked it, and the surprising thing was that at first level I didn't feel like I totally sucked.
My overall impression of the books is a return to 1st and 2nd editions where you chose a character class and stuck with it - though the multiclassing option looks flexible and useful if you want to mix things up. Paragon paths (at 11th level) look very interesting, though I'm underwhelmed with the Epic Destinies so far. Of course, it will be a while before our game gets that high, so I figure a splatbook or two will be out by the time we get there that will have expanded the options.