I still carry my glass carboys (3, 5, 6 gal, full) up and down stairs. No bueno doing so after having "samples" one's product, though. One of the biggest gifts was learning from Steve about the milk crate thing. I had a few holding scrap wood, auto parts, misc. Now they are all carboy holders. Looking for more, but they are rare here.
I think one of the other biggest benefits of the AIO is that it sucks out a good portion of oxygen from the receiving carboy (replacing with CO2 from the product being transferred) thereby reducing bad effects of oxygenation. That in itself is worth the price of admission. Of course I've used the AIO for the entire time I've been brewing/winemaking/mazing seriously.
I will say it's important to have blocks of wood or old encyclopaedias ready to raise the source carboy while its liquid level falls (in relation to the level of the bottles being filled) during bottling. Doing so a few times reduces the suction necessary (for beer, especially) and helps foam from forming as much, which otherwise leads to imprecise bottling levels.
A drop of mineral oil in the vacuum release valve will help it move more fully as it wears, and seal better when released. Not an issue when new, but they do wear. Mine is 2+ years old, functional, yet leaks unless I compensate for it.