How you pack a wheeled bag is just an important as the bag itself.
Put heavier items towards the bottom of the bag (near the wheels) and towards the back (near the telescoping handle when standing upright.) It's just basic physics. If you put heavier items up top, or in the outer compartments, the bag will have more of a tendency to topple over.
For some, a four wheeled bag will be preferred because they think it's easier. In some cases it is and in some it's not. They are generally heavier due to the extra weight of the additional wheels. They also don't generally move as smoothly on uneven surfaces because of the smaller wheels.
The way to test a bag is to stand it up. If it doesn't topple over when empty, it shouldn't topple over when packed unless you have too much in it or it's packed wrong. In most cases, it's the packer and not the bag.
For those who think pulling a bag is just too much effort and they don't want to exert any, there is a new bag that may be of interest to you. It moves by itself. You wear a small device and the bag will automatically follow you. It's not ready yet but I've seen prototypes.
There are also new bags being introduced this week that will charge your devices via usb, play music, use gps tracking to help find if lost, and act as a wifi hotspot. Some have built in seats and desks.
I think I'll stick with the basics. A bag that will get me from A to Z without any of the frills.