In addition to what was mentioned above, look to see if there is an owner's forum for the brand you are interested in. Many of those are independent of the manufacturer themselves. For example, I own a Grand Design product, and there is an associated user forum at:
Grand Design Owner's ForumUsing that same example, there is also a Facebook page for owner's of Grand Design products.
Grand Design Owner's Facebook pageAs mentioned before, you need to understand that most posts tend to be negative because somebody is experiencing an issue. Given that fact, you can then see if other owner's are experiencing the same issues, and if the manufacturer is addressing the concerns adequately.
Jim