I started a new game with this mod and skyTest together and it is amazing. My mod setup was basically Step 2.1.1 + updates and this was the highest priority. You don't even need Deadly dragons as they are a pain in the butt.
So far I've just played necromancy, with a side of light armor and light weapons. Each tree has what feels like its own spec. For example with light weaponry, you have the option to dual wield, 1hand wield (with a spell or torch offhand) or use a sword and shield. The conjuration tree lets you focus on summons, lets you collect and create skeletons, or raise the dead.
I've had no CTD's so far. I'll update if that changes.
Also for some reason I get mammoths that soar into the sky and meteor into the ground, killing themselves. It happens pretty frequently.
After a few more days I'll check out the vampirism tree and mesh that with other things. Maybe I'll try to do a full review. I want to be more active in helping with STEP.