Lightweight. Zips completely shut. Small, zippable external compartment that is large enough for boarding pass and passport, so you can have those handy for TSA, lounge, and at the gate, then put them away once on board. Large enough for a wallet, small amount of jewelry, iPhone, iPad, toothbrush, and meds (the stuff that you absolutely must carry on with you, even if there is no room at all for even the smallest carry-on suitcase). Small enough to fit under the seat in front of you. Large enough to work as your "personal item," rather than just another purse, small enough to work as an everyday purse during your trip. Neutral, minimal to no branding.