Spiral Knights is a good time killer with friends. But it does have a huge flaw.
The whole energy system. You start with 100 energy (basically, the currency of the game..but not for buying items) and it depletes from crafting items, going down levels in the Clockworks, and reviving yourself when you die. This is a huge flaw because it makes game play very, very limited. If you conserve your energy, you can basically only go down 10 levels a day. You regain energy at a rate of 1 energy every 13 minutes. Which basically means to fully replenish your energy, you need to wait 24 hours.
This is extra inconvenient because yesterday when playing, me and Ralren finally got down to a boss. We couldn't take it on our own..we needed more people. But we died. Yeah. We just spent at least 50 energy for it. But we had a lot more because we did what I'll go over next.
The game is very sneaky. You have to pay real money to get more energy and fully enjoy the game. He paid 5 dollars to get 750...which isn't bad, but if you really want to enjoy it without worry, you'll have to shell out at least 20 dollars to get more. I'm sure there are plenty of MMO's in which you need to spend a bit of cash to unlock stages or features or whatever, but in this game, it seems spending real money is a necessity.
I'm suspicious that they made the boss extra hard too so there will be barely any chance of survival, so you have to do it all over again and waste energy so you have to buy more.
Other than that, the game is a good time waster. I like the gameplay a lot. I'd be full satisfied and play it more often if it weren't for that flaw. In a way, I guess the game isn't free, haha.