Hi EJ! Sorry for not being timely with my reply...got caught up with the demands of work, etc. The yaktrax work admirably well for me on standard regulation trails of, I'm guessing, 30% or less; some short sections tend to be considerably steeper. A previous writer stated that they slipped off his shoes; I have not experienced any problems with this, neither going up nor coming down. The grip was good, but then, the surface hasn't been pure ice, more like compacted "almost ice" snow. I don't think I'd trust 'em on an incline of ice. They're not crampons. Another writer said he used them going up a rock escarpment and they crapped out. They're not ment for that either as they're not technical gear. Basically, what you have are some big wire-wrapped rubber bands!
A lot has to do with the mechanics of how you walk. Some folks can go uphill on their skis while others just slide back. It all depends on your forward lean, foot placement and other intuitive parameters. So all these various ice walkers can allow you to be more sure-footed, but that doesn't mean you can throw caution to the wind.
As for the Grivels, I was mistaken. The G-10s are my steel ones. The aluminum Grivels are called the Air Tech Light crampon. So far, no problems, but since they're alloy I'm careful to keep them out of the rocks. Hey, how the heck do ya get rid of this stupid pencil?