Lots of people have had opinions about this, and it ties into some interesting discussions about whether governments should subsidize art, whether their games were good, whether they were games at all (that endless debate), and so on. Since I am apparently one of fairly few people who have tried the game, and my opinion of it is so different to many other people, I thought I'd try and respond specifically to some of the criticisms I've seen of the game - not necessarily trying to counter them, but at least explaining why they didn't occur to me, or if they did, why I didn't think they mattered all that much. You could loosely consider some things below as spoilers.
However, I can fully understand how people looking for a more 'typical' game would be turned off by the problems raised above. It wasn't polished in a gameplay sense, and the mechanics were not immediately intuitive to me. They weren't hard to figure out as someone with a lot of gaming experience and having read the FAQ in the game so I knew what I was looking for, but it was not as smooth as Gone Home. I think they did succeed in making something that could appeal more to a regular gamer (I did kickstart it, after looking at their previous output with interest but never quite the motivation to buy anything - a position I might change soon, just to see how Sunset compares with their past games), but it's still an art game at heart, with all the foibles and jagged edges that entails. Some might even accuse it of being a wolf in sheep's clothing here; taking on enough of the trappings of first person exploration games to pass as one, before revealing itself as a rather different creature.
Finally, there have been people calling the story and general atmosphere clumsy, pretentious, and otherwise lacking. I don't really have a lot to say about this - Sunset touched me more than I expected for reasons I can't quite elucidate, and while I can recognise some of the points people have made, they just don't fit with the experience I had. My mood while I was playing the game was in tune with some of the topics it was exploring, and I'm sure that's a major part of why I got so much out of it. If I'd been feeling differently when I decided to start up the game, maybe it wouldn't have got its hooks into me like it did.
As with any artwork, something like Sunset is always going to be partly defined by the emotions of the person viewing it. With games, you can take a somewhat subjective view and admire the mechanics or technical craft running things behind the pretty exterior, but Sunset doesn't have anything substantial to offer there - it's a game, but only because that's a good form for the arty aspects which are the real point. You can't approach Sunset like a regular game and expect to get anything much out of it - the artiness shines through, and I suspect that's why it hasn't sold much despite more conventional trailers and trying for more accessible and traditional interaction. People can see that, and for better or worse it seems that a lot of folks who play games aren't especially interested in trying games like Sunset. I'd say that's for the worse, but then I haven't bought any of Tale of Tales' previous output either, and I forgot that I'd even kickstarted it or why I had until I got an email about it being released. A case of physician, heal thyself, I think. There's no shortage of indie and artsy games out there, they just want an audience.