My two sons have been playing Torchlight II (with the blood splats turned off) and are having a great time with the solo game. They've been begging to group up and play together, but the game's out-of-the-box multiplayer capabilities are useless. The first 4 times I tried to set them up for internet play our router crashed. I've never had that happen before with any other game, so I didn't realize what was happening initially.
Now, I'm going to have to dig out an old router and set up a lan game for them on the internal network that I can safely disable all the security on.
Despite the game's high entertainment value, I feel like the online play aspect was completely neglected. I believe the game uses UPnP exclusively for multiplayer without any other options for route traversal. I haven't researched the issue very long, but frankly, I expect modern games to work out of the box.
I give Torchlight II five stars for single player fun and zero stars for multiplayer. Once I have my book safely out the door, I plan to spend some quality time with my boys playing the game, but I really hope that we come up with a better multiplayer solution than hooking up to an old router.