Programs: Amex Plat, AA, BA Silver, US, WN, SPG Gold, Choice Plat, HHonors Gold, Marriott, Club Carlson Gold
I think the Train Reaction works well, but it's not a panacea. Lighten your packing first, then consider the use of such a device if you need that many bags. I bought one (well, two on a 2-for-1 deal) that I have used on several occasions when I've taken a golf bag on a trip. If I do that and don't have to worry about the cramped space in a regional jet so that I can take along a rolling suitcase, the Train Reaction works just as advertised.
But short of that kind of packing, you're much better off to reduce the amount of your packing, reducing your load to one or two bags that don't need to be checked. From my personal experience over the past year, I've been able to reduce my packing to a very small level, even on a 4-day trip, to the point where I take nothing more than a small backpack (1400-1500 cubic inches) and a generous, but still within all the published rules I've seen, personal item into which I stuff a netbook, all my electronics, and a full change of clothes.
And, to a cetain extent, I think if you buy the right types of clothes (pack some tech fabrics, especially underwear that takes you from packing a week's worth of underwear to one or two pairs that you can wash in the sink every night) and take the right kind of attitude (as the old saying about death goes, you can't it with you; that saying should apply doubly to travel on planes), you'll find you have all you need without the need for extra gadgets.
Bottom line, you probably don't need it unless you're taking something, like golf clubs, that you cannot take into the passenger compartment with you. Then, when you might be looking at hauling two or three bags, it is worthwhile, especially because it's a fairly inexpensive gadget (although probably still overpriced). Even then, you must use a rolling bag to get any benefit from the Train Reaction. If you carry a backpack and a duffel/tote/computer bag w/o wheels, I don't think you'd see any benefit.
I travel more than 100K miles per year on biz, and almost exclusively with carry-on-only with 7 days worth of clothes (+workout runners) in my 18" Briggs & Riley. Wear the suit jacket (pack-n-roll the pants) when flying (easier to do when travelling in J class but possible in Y subject to overhead bin space) so that it doesn't get wrinkled. I even got my entire family travelling carry-on-only for the other 15k miles I spend with them. The only time I checked in bags in the last 12-months, my B&R got diverted to Ottawa (from Toronto, after a trip back from the Caribbean) instead of meeting us after the flight to Montreal.
I am off to Europe next week. It will be carry-on-only.