Yehey! It's fnastastic!
It's pretty much just more of the same, but hey, when "the same" is so darn good it's hard to not like the new bits.
I got hold of a collector's edition the other day, going to have to work out if I can still get the extra in-game pet despite first entering the non collector's edition serial numbers.
The expansion came with two new races, "dranei" and "blood elves". The dranei are supposed to have crash-landed on Azeroth with their space ship(s), so they have a slightly more high-tech version of start-up area than the other World of Warcraft races. I just had to roll one to see for myself, despite it being an "alliance" character (two fractions, fighting each other - alliance and horde). :-)
I best log on and continue to play.