My husband and I, my sister, and one of my employees all fly with in-cabin dogs fairly frequently, on United, Alaska, and Delta. All of us travel with a wheeled carry-on (either a rollaboard or rolling computer bag) and a Sherpa bag. None of us have ever had a problem at security or getting on the plane. We've never had a discussion of which item was the carry-on and which was the personal item. The only problem has been trying to have three carry-on items (rollaboard, Sherpa Bag, purse) -- sometimes this works and sometimes it doesn't.

There is no way I could lug the Sherpa Bag around airports without putting it on a wheeled bag.

We use the over the handle Sherpa bag accessories (I guess they don't sell these anymore), stuff the back pocket quite full, and sometimes even put a purse into the main compartment with the dog. We're all usually combining dog travel with business travel so we're carrying laptops and meeting materials. Plus, we've been stuck at airports overnight with and without the dogs, so we make sure to carry emergency clothing and dog supplies.

We have essentially the same carry-on items when we travel without the dogs except that the Sherpa bag is replaced by a similar-sized tote or duffel. We've never been questioned about these carry-ons either.