No go on the boot bag as a personal item. Maybe you guys have just had good luck / gotten cool airline personnel, but anything larger than a laptop/DSLR camera case/purse/plastic bag full of magazines means you risk having to check it (and pay). Ski boots are WAY too big to get as a personal item in addition to a carry-on bag.
On the flip side, Never, ever, ever pay to check your skis. I've been charged multiple times, and have thrown a fit, and always been reimbursed by the airlines. I now carry a printed copy of their policy explaining that skis and golf bags are not to be charged oversize baggage fees (those are reserved for surfboards and bikes!).
My setup is:
-A two-ski bag with poles, clothes, hat, gloves, base layers, fleece, etc. Basically as much as I can fit in the bag, and I don't think it would be possible to go overweight given the limited size of the bag. I have a rolling one I really like (I think it's from Dakine).
-Carry-on my boot bag with favorite goggles, Ibex 3/4 length baselayer pant, ski pants, boots, helmet.
-Wear my ski jacket, laptop with personal items in case.
I can usually get away with shorter trips like this no problem ,which means no paying for a second checked bag. On longer trips, or if I'm flying with my wife, I check a second duffel bag. She's United Premier-All-World-Ninja-Executive, so she gets, I think, 3 checked bags for free per flight. Plus we get economy plus seating and preferred boarding/baggage handling. No, you can't borrow her for your ski trips (unless you want to pay for my plane and lift ticket, in which case, sure!).