I've been waiting to review a product for awhile now, I've been trying to put my name out as a good honest reviewer. I would love to review this piece.
But to refer to your question regarding only working with herbs, it's internal components might not be made for gooey expanding concentrates that make big bubbles and such. Although you could probably jerry rig it to make it work (put cotton in the bowl and surround your concentrate with it), it's not recommended. You can get a perfectly good oil pen for that.
oils is definitely harder to get a hold of. I am not about that life. Just the regular shit. A dime bag with some dry herb. but i commented on the zenpen website, we've gone back and forth they're real cool. They told me that the pen was made especially for dry herbs. hopefully it's true.