As is my wont, I have now restarted the game more than half a dozen times to try out different approaches and methods before settling (back) down to my usual assassins. I have not seen it all, nor done it all, but I have sampled many zesty dishes before returning to safe and well-traveled ground.
Thoughts on ...
Magic: much better than Oblivion. The lack of custom spellcrafting does limit your options, but it also puts most game-breaking combinations out of reach. Illusion, a favorite/least favorite school, has gone from abusive to merely awesome. I love the fact that while there are perks that will subject even the highest-level NPCs, along with atronachs and the undead, to your wicked wiles, at least one class of reasonably deadly foes is forever out of reach. Accursed dwarven automatons!
I love the "overpower" effect for dual-casting the same spell; there's nothing quite like charging up a double fistful of destruction for the next miserable fool to round the corner, but for me the most important improvement to the magic system is simply this:
It feels like magic.
In Oblivion, you pointed and clicked. Click, whoosh, your spell was cast. Boooooring. This time? This time, absent a "continuous casting" spell, you must be patient, grasping and gathering in eldrich forces. It takes a measure of patience and control to hold your fire and let the power coalesce in your hand as a hulking orc charges with dwarven warhammer swung high to stave in your poorly-defended, low-HP skull.
Beautiful. Just beautiful.
Complaints: broadly valid, but useful in inverse proportion to their inevitability. Bethesda makes huge-ass games that are, by necessity, very loosely joined together. The storytelling is never, ever going to be tight, plot-related absurdities will always abound, and the fact that this is possibly the LEAST bug-riddled product Bethesda has released is saying a great deal.
As for difficulty: Master difficulty is apparently un-playtested in a way and to a degree that makes it second-cousin to unplayable. That's annoying, but I don't play TES: Anything for the frantic challenge of it. I play them to have a world to explore, and when immersion breaks down, as it almost inevitably must, I make a new character and go explore something new.
I do not want a TES game to kill me regularly, because, in TES, if I die, I just broke history. Death in TES should leave me with the sense that I really, actually blew it-- and generally, it does.
As for Skyrim being "dumbed down," I found the allegedly more limited interface vastly more engaging and vastly less open to abuse. In Daggerfall, I could, and did, create a totally magic-immune character who could spam max-statted fireballs at his own toes, instantly reabsorbing the magic only to send it lashing forth again, a class I named the "Vortex" for good reason. Morrowind allowed me to trivially brew potions of intelligence, which reinforced my alchemy skill for making my next potion of intelligence, which ... and so on. Pretty quickly, you could make potions of I Am A God.
Skyrim, to its cost, did not escape this last dynamic entirely. Alchemy reinforces enchanting, enchanting reinforces alchemy, and both alchemy and enchanting reinforce smithing, such that combining all three does indeed allow you to once again stride the land like a god (your only true weakness being plot points that strip your equipment). Not my cup of tea, but I also don't find it entirely reasonable to ask a game of this scope to provide me a challenge if I choose to configure my character in such a way as to deny myself one.
If I want a serious challenge, I go play Dark Souls, where a miserable tapestry of attempt, failure, death, resurrection, and reattempt is the entire field on which the game is played. THAT is a good game for the proud and the masochists amongst us.
... And it's primarily a console game, by the way.