Crystal tower right now has one level only (can't wait for more).
Since it's dropping very nice loot and is relatively easy. A lot of people are spamming it until they get the drop they want, which make it a bit repetitive, but hey, everything will become repetitive if you do it 5-10 time a week for 2 months
Also, since it's quite easy to complete, the biggest challenge will often be the players themselves, with 24 persons, they will often be a player new to the instance and also impatient players who doesn't want to wait for explanation to be given. (or simply some player trolling) It often create a bad ambiance for everyone.
All in all, CT is created as a boss gauntlet, all with different/interesting mechanics. When everyone know the mechanic, it's really easy, you can complete it even if the whole alliance is fresh out at level 50. But because of the same mechanic, if one or 2 players make a critical mistake at the wrong time, it can wipe the entire alliance.
Personally, I quite like CT for all the different kinds of fights. I would have liked a bigger challenge (like more random fight, with less scripted, predictable stuff happening) that would force the whole 24 players to work as a team.