Sometimes during testing, testers are asked to check out a specific feature and give feedback on it. Good, bad, ugly - developers usually want it all. First impressions, problems, overall feel, then down to the nitty-gritty on if something works right when it's clicked.
We had a feature we were looking at for a little bit and there was quite a bit of feedback about it, including many suggestions on how to improve it. It turned into a pretty lengthy discussion, with developers hopping into it with specific questions and commenting on a number of the suggestions. It was a pretty awesome discussion, and it was really cool to see the developers get in there and actually discuss it with the testers.
Not too long after, we were asked to test it again - this time after suggestions from the group had been applied to the way the feature worked. Not only did it greatly improve the feature, but it was done extremely quickly. I was impressed with both the speed of the change and the way the team interacted with the community, throwing around questions, answers, and suggestions to get a better feel for what would work best. And they did a great job in tweaking that feature to improve it.
This is one of the reasons beta testers are helpful. It's just so great to see a dev team hop into discussions like this rather than sit back and just collate the data afterward. The interaction with the testers lets them get to the meat of any suggestion or issue very quickly, plus it fosters a close sense of community. This was excellent work by the dev team and the testers improving this feature for everyone.