(also posted on uk.rec.walking newsgroup)
Sorry this is so long!
I'm one of those unfortunate people who has a problem with over-pronation of my feet when I'm walking. The Superfeet insoles helped somewhat, and I've since had custom orthotic insoles made with even more arch support. These are fine for most footwear, but sandals (proper ones for walking!) are obviously a problem...
Recent discussions on uk.rec.walking encouraged me to try the Chaco and Teva Terra-Fi sandals, with the Chaco ones in particular known for their good arch support. I also have very wide feet, and according to Peter Clinch (thanks :-) ), the Tevas are quite wide.
So off I went to the local 'Snow and Rock' to try both. As luck would have it, they had a pair of Terra-Fi sandals on sale for £20. These fit quite well and had reasonable arch support by the standards of sandals. I tried the Chacos but, while the arch support was good, they were too narrow and didn't seem as rugged as the Teva ones. It turned out, however, that the reason the Tevas were cheap was because the design has been updated. So I tried the new version, and was pleasantly surprised :-) The new Terra-Fi has much more arch support than the older version. I'd say it has considerably more than a pair of Superfeet insoles (although of a slightly different shape), and nearly as much as my custom orthotics. They also (as with the previous model) have a decently solid sole and a good degree of strap adjustment. Needless to say, I've bought a pair.
I've not worn them for a walk yet, but if you suffer the same problems as I do - try the _new_ Terra-Fi! (The patterns on the box are a blue colour, whereas the old ones were something different).