Valve has added a section to Steam to allow for user reviews.
Currently in beta, this feature allows users to rate any title they've played, as well as give feedback on other users' reviews.
If you find a user whose reviews you enjoy or agree with, you can follow that particular person's review portfolio and check out their take on other titles as well.
Valve noted in its FAQ that these reviews won't create an overall score or rating for a title yet, but it's looking into adding that feature during the beta. "Many products on Steam change significantly over time as the game or software is updated and new content is added. In order to form a score that accurately reflects the current state of a product, we first need to gather and evaluate the data from reviews," Valve explained.
Steam users will be able to write a review of any game they've launched and it will say next to their review how many hours they've put into it.
Since Steam games are often updated, the latest reviews for a title will be shown first to most accurately reflect a product in its current state.
For more information, check out Valve's announcement page dedicated to this new service.