I played it on the PC and have tons of mods for it. Some quests are pretty boring, some make you use the slow wait option for too long (Glarthir), and I got sick of the Oblivion gates ever since I entered the first one.
Otherwise, I play the game pretty often. Right now I modded the game so it takes a lot more stolen goods to get the next Thieves guild quest. It's too easy to reach the 1000 Gold you need to get all the thieves guild quests, I got 8000 without much trouble. I also have the Thieves arsenal mod which adds arrows which makes noise to distract people, a blunt weapon that stuns people but does no damage, rope arrows and more.
Otherwise a lot of the mods I use are just for looks only, like clothing mods, adding a Dwemer airship, adding stuff to the terrain, boosting up the graphical quality, stuff like that. It was a mistake to have an Adrenaline mod which boosts the amount of enemies you encounter in the world with a Thief character. I did get a gun mod though so if I just don't feel like fighting with normal swords, I use that and one hit KO stuff. And a bullet time mod just for the fun of it as well as a combat animation mod. Get some shields that look like off hand weapons with that and it looks like you're fighting with both weapons. One of the most useful mods I have though is one that allows you to carry everything you want. I can't go without that mod.
Open Better cities is nice too, but I want to wait until I'm done with the main guild/plot quests so that it doesn't interfere with them.
Also, for some reason I messed up something and now every crab is giant.
I like some of the clothing and rewards you get from Shivering Isles, but on a whole I didn't like playing it. I haven't tried Knights of the Nine yet but it doesn't seem too interesting to me. I just get mods to allow stuff from Shivering Isles to be sold in Cyrodiil.