My daughter got three of the little rats for Christmas last year from various relatives and my husband and I bought the little house and a couple of the attachments for them to run around in. She played with them for about a week and then stopped. She still plays with the house though. She puts marbles in it and rolls them through the connecting tunnel.
Also, when they turn on, those wheels go and don't stop unless the button is pushed again so my little girl picked one up while it was still running to give it a hug and the wheel caught up her hair and just kept going and going like it was crawling up to her head, winding her hair tighter and tighter into the gears. We had to cut it out. She never hugged it again and that was about the time she stopped really playing with them.
The extra accessories were mostly a flop. We got the wheel that they run in and if more than one try to use it they get stuck. The swirly slide is just awful because it let's the little things escape into the house! Any addon that allows the zhu zhu get out of it's self contained little area is bad news. They will go find the carpet and get hair and fur caught up in their wheels which will break them. They'll get stuck under the couch. The'll get LOST. The cats will find them and try and eat them.
They are really cute but if I had to do it again I'd just skip it and get my kid a wooden marble run.