Yikes.
I finally had to cave and join a faction/guild/organization, which I've been putting off for a long time. (I've got each and every one of them at the laaast possible stage before it commits me and flags me as a member of something....)
Surprise! I'm a Thief! (However I intend to eventually be a member in ALL such groups in Skyrim, BTW. Next will be The Dark Brotherhood so I can train in Alchemy.)
I had to do it because I needed their higher-level Trainers to get that last bump to 100 for my Sneak and Archery, which I've now done! (Lock-picking(92) and Pick-pocketing(78) are coming along nicely, as well...)
I wanted to find out from others, tho: Was the Thieves Guild/Nocturnal/Nightingales quest line as long for you too? It just seemed to go on and on. I'm on the part to return the Skeleton Key now and it's kinda getting tedious.
And while the Nightingale's outfits are cool looking (see below), I find that I've set it aside for the stuff that I was already wearing. (To whit: I find it "more stealthy" if I can one-shot kill one-by-one from stealth with my bow and its buffs than trying to "sneak" in to a group of Falmers and take them down.
)
Nightingale Thief Garb