Got the SIGG model that holds 0.6 Liters. That's 0.1 Liters more liquid than the 0.5 Liter plastic water bottles. So far, so good despite some minor drawbacks compared to the disposable plastic bottle: Aluminum is less forgiving on the teeth (using the screw top). Transparent aluminum hasn't been invented yet so it's not possible to glance at how much water is left. The outer surface is more conducive to condensation from cold water from the cooler. Reusable containers need to be cleaned, periodically. This particular SIGG bottle also doesn't fit as well in the back jeans pocket although the ringed screw top is easy enough to loop around a finger. It would be nice if the screw top took fewer turns to un/screw.
On the bottle-is-half-full side, the SIGG looks cool, a model of Swiss design. Using one elicits a warm and fuzzy feeling that fewer plastic bottles are going into a landfill. It can probably be used as a blunt weapon if needed yet it's still about as light as a plastic bottle. Most importantly, SIGG bottles aren't susceptible of leeching chronically toxic bisphenol A (a.k.a BPA) into water like their plastic counterparts. BPA bad!
