I have yet to play it, but in my opinion, it must be decently successful if it has managed to keep rank 4 on xfire constantly. I don't think AoC or WAR lasted more than a few days on the top 10. Yes, I know not everyone uses xFire, but it tends to be an accurate measure of time played.
It seems it's had ~20-30% of World of Warcraft's daily minutes.
I'd like to try the game for myself, but anything that isn't Guild Wars will A) Cost money I don't have. And B) Require time I don't want to spend on grinding no matter how much time I have(And I have a lot)
I may have lost interest, but when I pay for something monthly I feel forced to play use/play it or be wasting my money. I just pray Guild Wars 2's no subscription free and it's unique quest system ( among other things ) crushes the subscription model these money hungry companies love so much.