So Chaco makes some great sandals, and I have three pairs, and I have worn them all over the past week. The three pairs are each pretty different.

Z1 Uniweep (2005+ model) I got these on a end of season sale last year. These are supposed to be 20% lighter and it feels that way. They also combined two soles into one for these, though it seems more like the Terreno and less like the Colorado.
<%popup(20070509-uniweep.jpg|292|166|Uniweep Sole)%>

Z1 Terreno It might just be because they are 5 years old not but it feels like they have more cushion on hard surfaces like concrete. Mine also have no tead left along the ball of the foot and the strap is almost worn through at the big toes, but I still love them. I will have to get these re-strapped and maybe re-soled.
<%popup(20070509-terreno.jpg|178|178|Terreno Sole)%>

Z2 Colorado I am just going to come out and say it: I hate the big toe loop. Sometimes I don't notice it, but when I do it drives me crazy. I spend a lot of time with the toe loop pulled tight against the footbed. I do like the additional control the toe loop gives me when I am kneeling in a canoe. I also like the thinness of the Colorado sole, especially the flexibility when under a canoe seat.
<%popup(20070509-colorado.jpg|178|178|Colorado Sole)%>