I live in Austin, and pretty much every bike has a u lock, for good reason. However, u locks aren't always convenient, and sometimes, I like to go on a training/fun ride and leave my bike somewhere while I go explore, read, eat or whatnot. I would like to get one of those combination chain locks that I can sling around my waist while I ride, and conveniently lock my bike up when I want to leave it outside a store for a while or something.

Anyone have experience with these? How secure are they? recommendations?