The automatic installing and updating makes it an automatic "no" for me

^This basically, because sometimes updates from Mods can break your game.
I sometimes check the workshop, but I use the Nexus-Link most people provide. The NMM makes it pretty easy to keep track of and manage your mods as well as install texture-mods without the freaking esp and bsa. (I've got 64 esps activated atm and with Texturemods that would go through the roof)
//edit
Also as a long-time Nexus-user (Oblivion, Fallout 3 and NV) I feel like it is my duty to support them and they had mods on their site quite quickly after release, while the Workshop was only added in February.
//edit2
Forgot to give you some mods (you might already have some of them):
Skyrim HD
Serious HD Retexture (Landscape and Riften)
Chris2012 Whiterun Textures
http://skyrim.nexusmods.com/downloads/file.php?id=5603
Warzones
PISE
Deadly Dragons (if you are into exploiting the crafting system and think Master is to easy, otherwise they might be to hard ^^)
Balanced Magic
Riverwood Redux
Female Muscle Mod (if you want women to look like the lore says they do, instead of supermodels, otherwise you might want CBBE or Demonized UNP. If so, I suggest taking Skimpy armors as well)
http://skyrim.nexusmods.com/downloads/file.php?id=13567 (enables you to use different body mods for different body slider setting)
XCE
Beauty Faces for Females
and before I forget one the most awesome mods I have
Hvergelmirs Armor Retexture
Hvergelmirs Shield Retexture