I haven't tried it yet, and to be frank Ladybirds first sentence scares me a bit (every time I hear someone talk up a game referencing only how they've 'removed the un-fun stuff', not how they've added stuff or replaced stuff I'm reminded of just how many sequels I've played over the years that had the 'unfun' removed only to find said sequel now had the complexity and 'fun' of a game meant for small children (see also: Mass Effect 2, for example. Stripped the Un-fun right out of that sucker, along with almost everything that made ME more than just a sci-fi shooter.... I notice ME3 went around adding 'unfun' shit right back into the game, to 'prove' my point.)
The mechanics that they have removed, are the mechanics that didn't work as intended. Diablo 2 was not a game that presented the player with enough information for them to make valid choices about the allocation of their limited in-game resources (Mainly, stat and skill points), and provided no way of rectifying poor choices short of restarting the character (Until they added limited respecs... last year?).
Manual stat point assignment, frex, was something that didn't work. If you knew what you were doing in D2, you took enough STR and DEX to use your gear, and put all your other stat points in VIT... unless you had an ultraspecialised build, in which case you knew exactly how to put your points, without deviation. If you didn't know what you were doing (For which, read "hadn't spent enough time out of the game reading up on hidden mechanics"), you'd put stat points all over the place, and wonder why you were dying so quickly later in the game.
In D3, you get small stat increases each level, and what they all do is explained for you so you know which to go for. But those are insignificant increases compared to what you'll get from gems, later in the game. And if you make a poor gem choice, you can fix it, without losing your best gems and gear.
Skill trees, again, didn't work - you needed to go outside of the game to find out how they all went together, and there were very few builds that could handle later stages of the game. In D3, new skills and runes unlock automatically as you level, and you can pick six active and three passive skills to use, like Guild Wars. They also level up with you (Actually, damage skills are based off your weapon damage), so everything is usable throughout the entire game.
What it adds up to, is that you can't get yourself into a position where your character will be unable to advance, and you have to reroll from the beginning. The amount of choice in the game has gone up, way up, because now you have the freedom to pick the skills and playstyle you
want to use... and if it turns out not to be effective, it doesn't mean restarting your character. The complexities - finding out what works for the playstyle you want, gearing up, understanding how and when to use your skills - are still there, just as they ever were, and you can still micro-optimise your character to a very large extent.
I do kinda miss having to identify items - blues are automatically identified, yellows aren't, and that is the highest I've found so far - and I think you should have to go to town to change your skills, but other than that, this is the game that D2 always wanted to be, but never actually was. Don't get me wrong, there are design choices I'd be iffy about in a tabletop game, but they work great for a video game about killing monsters.