I've looked at them over the years, and borrowed my brother's, but I've got to admit to liking the Guyoet stainless bottles better. Fells better in the hand, they don't have the neck so they are easier to clean, and they use the defacto standard thread of the large mouth Nalgenes- even easier to fill. And the cap is neigh on indestructable.

And it is looking like they are going to partner with Nalgene, so they're both doing something right.