I pulled the trigger on one of these a couple of months ago, and really like it. I use mine to tote groceries at the weekends, and it has carried everything I've asked of it solidly.

Yeah it was "spendy" and I could have done the milk-crate zip tie thing and been on the right side for years to come. But that track mount is just so convenient for taking off the bike and wheeling into the store with me.

I really don't use the fold flat thing, though it's very easy to do. However one small niggle, there are two black plastic pieces used for clamps just above the side handles, (see picture), detach completely and need to be stored inside the basket, easy to lose. It's not a big deal to me, but hopefully they design that better sometime.