I don't see a reason to use racks other than Topeak's line. The track-mount thing is just too slick to ignore. I can put my basket or a trunk bag (or this TrolleyTote) on mine without turning a single screw or cutting any zip ties. It's also got a proper mount for my taillight (why any company manufactures racks without a taillight tab is beyond me) and the legs can work with the bungee-and-ring lower mounts of my cheap panniers.

I think this TrolleyTote looks like a good idea. I don't mind carrying my basket with me, and around here, the sidewalks suck and are crowded enough to make a trolley more of a pain than anything. But, if the locale is right, I don't see a problem with it.