I just got them today, along with others.
IBQ: WOW. It's not what I expected. Except: what you've heard about it being strong--that's all true. So open it outside or in your lab. But about the scent--amazing. I thought it was just going to be inky or smoky or just dark, or maybe unpleasant. But I quite like it. From my brief encounter with it today I perceived it as earthy and rooty, similar in a way to vetiver. But it reminds me (like isocyclocitral) of playing in the backyard as a kid. We were fond of digging holes for a while--maybe it's similar to that dirt smell. (In case you're wondering, isocyclocitral reminded me of the leaves on the trees in the yard, or possibly a combination of the leaves with pinecones. Kephalis smells a bit like potting soil to me--my parents had a big nursery/greenhouse when we were growing up, so I think of "peat" when I smell Kephalis.)
Isobutavan: Well, after smelling bicyclononolactone, methyl laitone in dilution and coumarin (I think all these are lactones--I don't know me chemistre), I expected it to be rather mild. At 100%, it's stronger than I expected. Its profile is something like "white chocolate/cream soda with an apricot nuance, lends a thickening rather than a powdery effect." OK, sounds cool. Anyway, at 100% on a piece of paper, it smells like paint. But I get the creamy/slightly fruity tone behind it, and as it evaporates and weakens a bit, it definitely smells much creamier. In that "damn, this smells delicious!" creamy kind of way. Incidentally, I also got some ethyl vanillin today, and it's fantastic. Love it. Knew I would.