I'm one of the users that still use the old comment system, so for me you didn't change much in 2011. But since you implied that that won't be an option this time, users are not happy...
I would have expected you to make the beta feature complete before pushing it on 25% of the users. Then the feedback probably would not have been quite so negative.
If you wanted feedback on the design aspects I would have expected you to make a story about it, asking for feedback, like last time. But for a second round of feedback I would have expected a changelog, with details of what was done with the last feedback.
You can not get any other feedback from an incomplete site than on the design. If you want feedback on an incomplete site you have to give a big disclaimer before asking people for feedback, detailing which parts are still incomplete, and how they are planned to be changed. You can not just push something functionally broken like that on 25% of your users and expect anything useful.