Given a proper way to speak their minds and more ways to vote with their wallets, this is what PC gamers can do. If Steam had had a refund policy when Unity came out, I think a lot of customers would have asked for refunds and Ubisoft might have gotten the message they can't release broken games on PC, or lazy ports of console titles.
This is both good and bad, as it might make developers think twice before releasing a buggy game for PC again, hoping "gamers will eat it all up as long as we mention some kind of patch" -- apparently, what was wrong with Arkham Knight couldn't even be fixed by patching, there's also that, but let's not delve into it, for illustration purposes --, but this also means developers might end up simply refusing to make games for PC altogether, because it's easier, cheaper and more reliable developing them for consoles only. Plus, most of the money they get comes from the console market, not the PC one, as most PC gamers end up waiting for heavy discounts in order to buy games, whereas the majority of the console user base buys them full price for $50 or $60 -- even when discounted, in "GOTY", "Platinum", "Player's Choice" or whatever, a console game still costs around $20-$30, signifficantly more than the "ludicrous" $5 or $10 you pay for PC games during sales (sometimes even reaching $1 or less). For better and worse, the console market is "where it's at", for developers and publishers, even GOG's/CD Projekt's Marcín Iwinski said to Eurogamer
that «If the consoles are not involved there is no Witcher 3 as it is», and that «Developing only for the PC: yes, probably we could get more [in terms of graphics] as there would be nothing else - they would be so focused, like if we would develop only on Xbox One or PlayStation 4. But then we cannot afford such a game». So, it's a good thing PC gamers now have the voice and the power to show devs that they're not willing to accept broken games on their platform of choice, but we have to wonder whether this will be good in the long run or not, as developers might end up ditching the PC altogether, favouring the platforms they profit with the most, the consoles.
[EDIT] for the record, I know Steam isn't the first digital distributor to offer refunds, they are actually following in GOG's and even Origin's footsteps, but as much as we love GOG, let's not forget Steam is a huge behemoth that more and more people mistake for 'PC gaming' itself ("PC=Steam"), and they're still -- quite undortunately, maybe -- the ones that set the standards and lay out the rules. And GOG doesn't even sell most of these AAA titles, so... there's not much point in comparing them. GOG may be the second biggest digital video game store in the world, but the user number disparity is still huge.