I couldn't keep going - tried all the evil stuff I could think of that the game offers (necromancy, the Dark Brotherhood, siding with the vampires in Dawnguard and becoming a Vampire Lord) and it slowly svcked the fun out of the game. Sorry, Beth.
The Dark Brotherhood has some great benefits (Shadowmere, Spectral Assassin, Shrouded/Ancient Shrouded apparel) but the assassinations are painful. I'll have to make do without their stuff.
Being a vampire, as well as being a Vampire Lord, and siding with the Vampires wasn't as different from taking the Dawnguard as I expected so I couldn't finish (made it to Soul Cairn and quit before going to Blackreach). Also, the lifestyle of a vampire that I played (only out at night, not eating regular food) wasn't particularly enjoyable for me. Being a Vampire Lord is very powerful (gonna miss flying and that grip ability) but it's so separate from the regular skill trees and leveling mechanism that it felt detached ( like playing some other game).
However, I think it's a very good idea for everyone to try one or more of these flavors of the game for both variety and greater appreciation for the 'regular' PCs.
Next: a sneaky Khajiit illusionist who'll side with the Dawnguard, destroy the Dark Brotherhood, and clear all the bandit forts far and near. May possibly join the Thieve's Guid ('cause I love Riftin and the TG quests/perks).