Re Franco, I take it that polycryo is the proper spelling? For some reason I thought I had seen it as polycro, but I'm not sure where.
Bluefish, what sort of testing did you do out of curiosity? I did a few tests, with mixed results. Just attempting to tear it by hand it seemed to fare well, mainly stretching instead of actually breaking, unless I applied a lot of force. I didn't have any branches super easily accessible, so I ran a pen across a part of it stretched tight to simulate a branch getting caught on it. There it didn't fare as well. The first several times nothing seemed to happen, however when the pen finally did puncture it, it tore a nice half foot long hole, which of course easily widened with any force. I suppose that's where ripstop fabric has some advantages...
I'm not sure where that leaves it. Maybe a stupid light idea. Getting caught on branches is always a possibility, but many of the trails I hike are relatively well maintained, at least as far as branches on the trail... I also don't tend to do a lot of bushwhacking at this point.
I might go ahead and finish my poncho, since I'm half done with it, but I will probably only use it for weekend trips where the chance of rain is pretty slim (on the other hand, that covers a lot of my trips right now).
I'll put up some photos of the poncho when it's done for any who are curious.
If anyone has any experience with driducks and the like, I'm still curious how their durability compares to polycryo, since that seems to be the common criticism of those options.