I was having a lot of fun on my first day of Wrath of the Lich King. I went to a shop, bought two copies of WotLK (one for the wife), went home, and installed it without any problem. I got the impression that even if a downloadable version would have been available, the data transfer method of "DVD in car" is probably faster than the download would have been.
Anyway, I entered Northrend with my priest, and immediately looked for a group to Utgarde Keep. By the end of the day I had done 5 dungeon runs: Utgarde Keep twice, and The Nexus once, with my priest. And both dungeons once with my warrior. Lots of fun, interesting boss fights, and generally well made dungeons. Quest rewards included my priest already replaced three epics by blues, and he is still level 70.
XP in dungeons are good, but leveling isn't all that fast. I made half a level on the priest, a bit less on the warrior. What caught me a bit by surprise is that Blizzard completely changed their faction design: Neither dungeon gives any reputation points for any faction. So apparently I don't need to get to honored with some faction before I can do heroics, or run a dungeon just for reputation. I still might make more dungeon runs today, just for the fun, and the experience points.
I did a bit of questing on my priest, and some profession skilling up. Tradeskills in the release version are much harder to level up than in the beta. It used to be that recipes went from one color to another only when your skill reaches a number divisible by 5. Now you can go from orange to green in just 5 skillups.
All in all I'm quite happy with the expansion, even if I'm not sure how long that will last. But there is lots of new content, and only the burned-out see it as "more of the same".