I think blackreach is probably one of the coolest dungeons around. I personally have a negative association with it as on my first playthrought Lydia died in there, and later on J'zargo too. ;(
Ya gotta be reeeeaaaallll careful with yoru followers when in Falmer areas. The Falmer simply do not stop until their enemies are chopped meat.
Tell your followers to wait well behind, far enough so that they don't join in any fights. When you've cleared an area, retrieve the follower and proceed, then when you encounter more falmer vermin, back off, leave your follower, clean out the area, etc......