I second this! I personally tend to play browser games as first preference myself, so I suppose that's where my bias comes from. There's a lot less hassle overall and you don't need to jump through hoops to enjoy something simple. I can't speak for other players but I'd still be online and logged in after playing it and would usually remember to comment or rate. It's still fresh on my mind, after all.
Even a demo is fine - I've played demos on the browser and commented right after since I at least had enjoyed the demo version. I feel more people might consider buying or downloading a game if they could try it out on a browser first without any hassle to quickly make a decision. Sometimes I download games and forget I've downloaded them, only to discover I'd actually downloaded it weeks later, and have unfortunately already lost interest in it.
But if a web version isn't possible for a demo due to limitations, a free download would work just as fine, imo. Multiple screenshots also help if a demo isn't available. At least as a potential buyer I'd know what to expect, aha!
EDIT: THESE FORKING TYPOSSSSS