Ask HN: Is there a good discussion search engine?

Google's Discussion filter was immensely useful for filtering out all of the useless blog posts & reviews that would tell me nothing about a product or piece of software. Reading discussions from people who have or are using a piece of hardware or software was the best way to formulate an informed decision when comparing products. Of course, that search filter has gotten worse over the years with "-site:groups.google.com" being an almost mandatory addition to any query. But, it still worked great.

However, Google seems to be on the verge of removing that feature.

http://productforums.google.com/forum/#!topic/websearch/Psb6OmlLJTg[1-25-false]

It is no longer in the dropdown and to use it, you need to add &tbm=dsc. How long this will last is anyone's clue, but with it being removed from the dropdown list, I expect the filter to get worse over time.

So, does anyone know of a search engine that allows for searching similar to Google's Discussion filter? A search engine that focuses on looking for information in forums, comment threads, and places like StackExchange?