I haven't played spiral knights in ages, sadly. Aside from new games coming out, I sort of reached a wall with progression-- if I didn't pay money, I would need to turn to everyone else for crafting stuff, and it just kind of lost its luster. Still fun though.
Fair enough, although buying Crystal from other players has never been a big problem.
They've still been working on the game, though; it's more than just the Arcade now. Quite a while back they added missions to try and push a plot, and to give the game more purpose. If you're a fan of a halfway-decent story, it might be worth picking up again later on down the road when they've pushed it a little further (or if you're just curious how all the stuff they had before was supposed to fit together).