The City of Steam "closed" beta isn't as closed as all that. A swift google will soon find keys. Look, here's a thousand of them! Some bloggers even got sent them when they really weren't all that interested, with predictable results.
It's very much a real beta for all that, though. Not only do things change significantly from one stage to the next but the developers are as responsive, communicative and interactive as I've ever seen in any beta. They ask for feedback all the time and reply when they get it. When I post a list of bugs on the forums I get point-by-point answers, explanations or acknowledgements, as does anyone who takes the trouble to give potentially useful feedback.
Consequently, in the brief time I have been able to give each phase so far I've spent almost all my time actively looking for bugs rather than just taking the tour. It's a model of how a beta should be done, I think. It's not just limited to the forums, either. The devs are frequently to be seen in the game itself, clearly identified as such. This morning Refuge was positively overrun with them, so I took a few snapshots.