Haven't read the whole topic, but my general opinion is slightly split. I understand the premise behind Early Access, and as a developer, it is appealing. However, I do not agree with the way Steam implements early access, because I feel there is still a strong sales culture around the project. It feels less so about "supporting" a game, but rather just a means of buying a game early. Though this is entirely to do with representation.
For me personally, I do not plan on releasing my project on Steam early access, however we do want to run a Beta on GameJolt. The reasoning behind this is that the support is very beneficial, however I don't want the Beta to be branded as an actual commercial release in the same way. I would want it to be crystal clear that the game is still in development and that there is a chance it wont live up to expectation.
The big problem with Early Access is that it offers a bit of an escape route for developers, whether they are intentionally taking it or not. I firmly believe that most developers go in with the intention of finishing a game, however given how hard it is to estimate how long things take, normally it just cultivates an environment of disappointment. Eventually the developer may just run out of time, run out of money or just lose motivation in a long-term project, especially when it starts taking 3 years longer to make than they expected.
Though that aside, the biggest fundamental problem that I can see with early access is how it alters your process of development. IF you enter early access too early, it can severely impact your ability to work on your game in the way you want to. For example, every update you make has to be polished for release. I know that when I develop, it is far far easier to leave strings untied during the development process, and then clean things up later on when it is time to. The analogy I like to give here is that if you are building a house, but you keep having to paint a partially unfinished house, then later on, you have to drill the walls to do the wiring, you then have to go back and paint it all over again. Alternatively, some developers fall into a pattern of patchy development, where they realise this issue and because you don't want any update to be a step back, you just tack things on, without allowing yourself the room to make bigger sweeping changes.
So what tends to happen is that updates have to become infrequent if the developer wants to add any major features. Or, they just keep chipping away, making small updates, neither of which actually result in a finished game. Another good example of something that can easily go wrong is the save system. If you add a new feature, it may alter your existing save system, which means that each update breaks saves. This is fine if people have that expectation, but most people on Steam are just regular gamers who want to play games to have fun, only a subset of those actually appreciate what it truly means for a game to still be in development.
An early access system would be fine if Game developers did only use it when a game was far enough a long that no major engine changes would be needed, and future work would simply be the product of content development and polish. However, when a game is that far along, you might as well just wait for full release. Waiting for full release will mean a bigger initial impact (as the game IP hasn't been softened by having been out so long), it also means no bad publicity from mistakes you made in the past.
So, to summarise, issues exist on both sides. The perception of players and the misguided intentions of developers using early access for the wrong reasons, at the wrong time during development. Again, I don't think developers are intentionally mis-using the system, I think its just the product of mistakes that developers make. We all make mistakes during development, and especially for ambitious projects, it may seem like a good idea to release early to help support development, but you will just end up locking yourself in a hole, limiting the ways in which you can work on the project and that will fundamentally slow your development to a crawl, or even kill your projects potential.
Edit (A few more thoughts): To clarify, the tone of my post is supposed to say that most developers aren't these "bad" or "evil" developers trying to get a quick cash-in, they are ordinary developers like you or me who have not fully considered the implications of developing on a released title. Nor have they considered the potential impact it could have on the proper release of the game later on. (This is more to do with the idea that you want to snowball on release, get as many sales as quickly as possible so that your popularity rating gets boosted. If half the people who will ever buy your game buy it early, thats a big chunk from what could help an early surge).
The prospect of using it to "better" your game also seems less significant. Whilst it is true that feedback can help, this feedback can be acquired in many other ways that don't involve releasing it on a large commercial platform.