When did any of those became a problem?

Ease of use: you'll still be buying a game and putting on your console and playing just as well, it won't become harder to use at the slighest.
Stability and Guaranteed Performance: it didn't even released, how can we tell it'll not be stable or perform just as it have always been performing up until now? If anything the rumors are indicating the developers will have to deliver on both fronts.
Unified userbase: They'll share online gaming and the very same games, I don't see how that's a problem.

If some of this will change or become a hidrance, we'll see, but for now, it seems to have no problem.

What is pissing people now are the lost sense of privilege they have had up until now, now some are feeling like they own a not so good system, just because there is something a bit better coming, which won't make their PS4 worse at any level, though.

I'll get pissed if they do announce a GoW 4 for example and it'll be running only on the Neo or having issues on the PS4, then I'll get pissed, maybe even outraged, because then they are making the PS4 effectivelly lose something and harming their owners, which is not the case at all up until we got as news for now.

I was one of those unhappy with the New 3DS news.
Then we got no real problem with it happening, I've saw about the Hyrule Warriors game, but that's about it.
(the Wii ports didn't bothered too many people)

Now is wait and see as well, if it start having exclusives, or performance issues, people will and have to complain with both the developers and Sony as well.
Right now the news are good, and we have an example of that being acceptable by consumers with the New 3DS, which is now the most common being bought on the 3DS line.

Feels that way to me. All these years the power of the PS4 was totally fine and the games look AMAZING and the human eye can't see faster than 24fps.

But when they're suddenly presented with a better choice they start to feel inferior. Why though? If the current performance of the PS4 is totally fine and in no way underpowered, why be scared of useless hardware improvements that won't improve the games in any way?

If the rumors are true and there will be no exclusive content for PS4K then I can only conclude two possible things about people who hate it.

1. Money envy. They're not able to afford all the newest things and hate if other people can buy better products.

2. Hidden regret. They suddenly realize that if Sony apparently deems the PS4 too weak, they feel as if they were wrong all along and the PS4 is actually underpowered despite their furious claims.

Anyway I don't like it. For once Sony does everything right and is about to reclaim my lost faith in them and there are people who try to hate on it for their own selfish reasons.

Knock it off, guys. Let Sony be great again! The claim that the release of a better console version will in any way hurt the juggernaught that is the PS4 is ridiculous.

I don't think there should be exclusive, outside of maybe some indie games here and there, as you can't expect a really small studio, sometimes even just one guy, to do multiple versions, but even then, if that's the case Sony has to ensure that the developers always choose the PS4 to develop for, then both systems can play it, the PS4K may not make any extra use of it, but both will play the game.
If that's how it goes, and the PS4 is always the platform to develop for, there shouldn't be any problems.

While I see where you are coming from at the CURRENT moment your complaints are just not real. The uses base will not be split. Currently all games will work on both systems. PSVR will work on both systems.  The upgrades to the PS4K are so minor that they won't make a huge difference outside of possible 4K output for movies and TV. The people "talking" about how the current PS4 can't handle VR are just talking. So why are you upset? I don't get it?

The line between console and PC gets thin and that's what pisses me off. Those concepts I just threw are part of the "console philosphy" but the biggest (and most important) one is the one being affected. Consoles never need an upgrade, that's the biggest difference from a PC.

It won't matter to me anyway, I won't be buying the PS4k but I get pissed at the idea of consoles being similar to PCs. If I wanted to play games on upgradable hardware I would choose a PC.

As someone who's been gaming on PCs since early 90s and bought first one in '95:

I think there's quite a big difference between this concept of consoles and PCs - with PC, you're at the mercy of developers supporting your outdated hardware; with upgradeable/Mark II console concept, platform holder is guaranteeing you that your Mark I console will be supported and have all games working until next full  gen.

This is not even like upgrades of the past, where you had exclusive games for expansion (upgrade) - all games will work, if there was no PS4K, those would be only version of games on PS platform anyway, but since there's PS4K there is just another version with a bit better visuals - and that's about it.