I've played the shivering isles and I'm thinking less and less of it with each passing minute.
To me, the whole point of being in a "mad dimension" is to be enveloped by that dimension. Like some of you have said, this was a tremendous opportunity for Bethesda to draw players in and really make them feel like they're in some other strange and mysterious universe where you're always on you guard because "anything could happen at any moment" because this, after all, is a dimension of madness, where your own mind is your worst enemy and all that.
However, the world (an integral part of all TES games) feels closer to a cheap theme park. For example, take the two realms of the isles, mania and dementia. The "separation factor" is incredibly cheesy. You'd expect drastic differences between these places. What I mean is that you'd think that if you were in the colorful, vibrant world of Mania, all it would take would be a single step into dementia and the entire world would change under your feet. Weather, atmosphere, ambiance, mood, color, mindset, all that stuff should immediately shift into the darker, more abysmal and hopeless dementia. Basically, I expected the shift to be something like the movie "What Dreams May Come" where Robin Williams travels from his version of a vibrant, colorful, painted heaven to his scuicided wife's demented version of a dark, grey, dilapidated, static, oppressive hell.
Wrong.
Traveling from Mania to Dementia means that in the parts of the map that are supposed to be "Dementia," the grass texture changes to a little bit greyer color and the speed tree setting was turned from "big mushrooms" to "dead trees." The sky doesn't even change brightness or color. It feels like the exact same place, only with tweaked vegetation settings. Hell, you can even see the color of the mushrooms in the distance. Not a very separating effect. You'd think that if they had the "oblivion sky effect" for when you got close to a gate, they would try something with the same isolating effect, but they didn't. Very cheap and amature feeling, like walking around a county fair.
Oh, and something else that pisses me off to no end about the land in both Oblivion and Shivering Isles. Every bit of land in the world, aside from roads and town centers, is at least at a 30 degree angle. Bethesda were so fucking obsessed with realistic erosion patterns and making the land pretty for screenshots that they forgot they were making a fucking video game, where relatively flat surfaces are best for characters to walk on. I can't tell you how many times I couldn't look around and enjoy the sights or even see an enemy because I was using all my concentration on trying to walk up a damn wall of a hill by doing that thing where the land is too steep so you skid back and fourth looking for that exploitable patch of land that *will* let you walk up it. Bethesda, make the god damn land flatter next time around.
Sorry, didn't mean to spend so much time on just the aesthetics of the world, btw. Just wanted to give an idea of the incompetence going on here.
Also, I'm not too fond of the ruler of the realm, Sheogorath. He's too wild and active to be the ruler of anything. Very unconvincing. He seems more like the court jester than the king. This totally goes against at least my version of what he should be.
To me, true madness is the *potential* for total chaos at any moment, thinly veiled by the calm of your immediate surroundings, like waiting for something terrible that you just know will happen any second but hasn't happened yet. Totally unfounded paranoia. That is the feeling of madness to me. Sheogorath wasn't like that. To personify my definition of madness, Sheogorath should have been a more reserved individual, soft but steadily and intently spoken, with maybe even a hint of anger in his voice with undertones of "something just isn't right here," because that would leave the player guessing, and guessing leads to paranoia, and bam, the player might start to feel real apprehension and uneasiness, which is similar to the madness I was talking about earlier. Instead, he maintained the subtlety of a sledge hammer to the face and might as well had a neon sign above his head that said "Look how crraaayyyzzzeee I am! Woohoo! You never know what I'll do because I'm CRAZY AND MAD LOL!!!" I didn't really buy it.
Quests suck, too. Right now my character is on a quest to gather a type of ingredient from a certain type of enemy. Eating the ingredient will open a door or something, and I have to go through the door to continue on, but the enemy is incredibly rare and worse, the drop rate for the fucking ingredient is incredibly low. I've all but circled the whole damn island 5 times and seen three of the fucking enemy I need. None of them dropped the ingredient.
The ONE redeeming factor of Shivering Isles though, are the dungeons... or at least the one I've gone through so far. The atmosphere of the dungeons are great. Actually, the dungeons feel way more like my idea of "dementia" than the official land of Dementia ever could. They're dark, dilapidated, and indicidual chambers are sized just right between claustrophobia and emptiness, and the enemies are tough enough to make you fear them.
Overall, Shivering Isles is basically an exercise in looking at a product and at almost every point saying to yourself "Man, what lazy programming. This could have been done 100x better if only..." The thing that really gets me though is just how good of an idea the whole maddness theme is for a video game, and how hard the team must have had to work to screw it all up.