I'm a bit new to minecraft in general, but here's my impression so far:
Harvestcraft-not a fan, Kept filling my inventory with way way too much stuff. Turned it off for a second try after stranding myself in Mystcraft.
Did ATG both times. It's pretty neat, quite a different experience from regular biomes. Some irritants (soooo much mud at the shoreline) but in a good way.
A problem I have is that I have two kinds of marble now-one from artifice and one from some kind of exploration mod. It would be nice if they would combine and work the same way. (I like the one from artifice better)
Also there are two recipes for chiseled stone bricks, one of which gives you 4 times as many as the other.
I'm looking forward to starting up witchery though. And glad to hear that blood magic is off just for content reasons-if I start a third world I'll probably put it in.