Boneyard Scourge, Patron of the Vein, Vindictive Lich and Shifting Shadow didn't make the cube after all. First cube night with the new Commander cards that did make it in is scheduled for the 30th this month! I have been playtesting on Forge though, and Taigam is amazing! Curse of Opulence has been very fun as well, especially with
Makeshift Munitions from Ixalan. Mirri is good, and a cat, which has somehow grown into being a relevant creature type (I'm looking at you
Heirloom Blade and
Pride Sovereign!). Heirloom Blade is solid, so far it's at a power level that has proven to be very hard to find for WotC. Not every deck wants it, but in the decks that do, it offers a significant aggressive boost without making the cards too big to deal with, and the draw power makes sure you keep the pressure on, but because the card goes to hand it's not overbearing. Kess I have only drafted once, but she was very good. Very comparable to
Karador, Ghost Chieftain actually. Qasali Slingers is a replacement for Acidic Slime. I like the 3/5 reach body better than the 2/2 deathtouch, and killing lands is irrelevant in my cube. Khery Mind-Eater varies from cool (with equipment, when you play your opponent's colors) to feeling rather inconsequental (when you don't play your opponent's colors, when your opponent ran out of cards), but I guess it still exiles a card when it hits. I need to see it in action some more before I can pass a verdict. Scalelord Reckoner is pleasant. It's a good evasive threat that takes something with it when they deal with it.
The coolest cards for me so far have been Taigam, Sidisi's Hand and Curse of Opulence. Both have played much better then I expected from them!