That's what we've been discussing!
I've found them cooler and drier than a sweaty raincoat.
As to snagging, they aren't much for bushwacking, but you should be able to get down a trail. A little cord around the middle helps a lot. A driduck raincoat sure won't make it through the brush. A poncho will allow you to wear gaiters and improve the ventilation on your upper legs and drop the weight further, and chaps or rain pants are still options.
IHMO, I don't think much of open tarps unless they are something like 8'x10' or larger and I can't see where a poncho tarp is more than emergency shelter. A floorless tent, like the Gatewood or the GoLite Hut1 provides enough protection that a bivy sack or other work-around is not needed. A shaped tarp, like the GoLite Cave is 14oz and $110 and I'll have my dinner water boiling before you get your shaped tarp pitched. I've had sailboats with fewer strings!
The whole reason I use the Gatewood is weight, volume, cost, and multiple use. The Cape is $110 and 11oz. A Marmot Precip raincoat lists for $100 and weighs 12oz. I'm not going to do a cost comparison with the driducks as I feel it isn't an "apples and apples" proposition. A Granite Gear Cloud pack cover is 3.9oz and $25 and I got rid of another Granite Gear cover that was more like 6oz. A comparable tarp/tent would be something like the GoLite Hut1, which is $130 and 15oz.
So, I can spend another $145 and end up with a sweaty rain jacket, a pack cover that lets water run down my back and soak into the back of the pack, and a shelter that weighs more, takes two poles and 3 more stakes to pitch. I would haul another 19.9oz. Now why would I want to do that? <grin>
And then we can start throwing things like resources into the fray--- a lot more fabric, hardware, zippers, etc, etc, etc.
Is there compromise? Yup, but it works for me.