I haven't. Only got to play about a day of the beta and while I enjoyed it I don't think I can manage two mmorpgs at once, and I'm too tied here.
They are long for what they are, but still pretty short. Another problem is that there is nothing else to them other then getting to and killing the last boss. No npcs or quest deals inside them, nothing to gather, no other reason to be there except killing the boss. Every single quest that has to do with a dungeon also has that same goal, and they are designed that way.
I will admit that they could do more interesting stuff inside the dungeons. For example, while this wasn't a major faucet of Brayflox Classic, I loved how you had to rescue Gobbies by a certain time once you entered certain areas, in order to get all of the loot.
I'd love to see more stuff like that, with increasing complexity as the game goes on. Give us dungeons where we have to run into a citadel and rescue orphan children, then have to escort them out again. Or areas where if we come to the assistance of NPC's infiltrating the same military installation, they'll follow behind an assist with the Trash, up until you reach the boss.
Granted, this would be quite a bit more complicated, would require far more planning in order to make work correctly, and might be a bit risky in terms of possible bugs. Regardless, this sort of stuff would be fun, so it's a shame we haven't seen it yet.
Maybe further down the line we'll see more stuff like this. 2.0 was a bit of a rush job after all, and a large portion of the content we've seen since then has either been similarly rushed or half recycled. I suspect a large portion of their resources are going into content we won't be seeing until the next patch, so, hopefully we'll see interesting stuff like that around then.
Until then, eh, I'm having fun with it.