Comments about REI Evaporator Ski Boot and Helmet Bag:
My first use of this bag was a weeklong trip to Utah, so you will get my perspective of the bag as a day-use boot bag, as well as checked luggage. No issues in either case. Definitely plenty of rooms for a pair of boots and ski pants, but depending on the size of your boots and helmet, it could get a bit snug if you were to carry both inside the bag (I was able to fit my 26.0 boots and M Giro helmet, YMMV). I usually just clip the helmet to the bag when carrying the bag to/from the base lodge. The bag is not padded on the sides so I would not recommend storing your helmet inside if you were to check it in as luggage (it is padded on the bottom, however). Apparently some people just bring their helmet onboard the plane, which is not a bad idea. The side pocket is very useful for carrying gloves and that sort of stuff.
The bag has carry handles, a detachable shoulder strap, and backpack-style straps (tucked away inside another zippered pocket). I've only used the shoulder strap or the carry handles. If you're traveling with some other rolling luggage, you can loop the carry handles over your luggage handle and drag it around on top of the luggage. The bag has a windowed pocket for a business/ID card. The zippers sliders do not have metal loops for a luggage lock if you're concerned about locking up the bag, but the zipper pull cords can be tied together (and/or locked together with a lock) if needed. Overall I'm happy with the bag.
Bottom Line Yes, I would recommend this to a friend