Never really used them as review aggregator and gear choice aid; I change camera rarely (and never changed brand since 1999, so I wasn't interested in generic reviews from other manufacturers), while lenses I change often, TOO OFTEN, but my holy guide about lens choice has always been photozone.de! I have NEVER regretted a purchase based on their reviews.
But in the forums, skipping all the fanboy wars, I often found, via google search, many insights and tricks on camera, lenses and photo/video equipment in general, like when I was having doubts similar to "can I mount this first thing on this second other thing, and how this other third thing will react?".
So while I personally (again, personally) won't really mourn the "commercial" side of it, I will certainly mourn the HUGE loss of knowledge you could sometimes find is some forum post; It's a great loss of information and user experience, and I'm devastated by it.