I do have a woobie by Kifaru and a Wiggy's woodland camo poncho liner. The woobie is really "slick" that is, it's outer shell is a thin nylon that is surprisingly strong and lightweight compared to the previously mentioned "stiffer" Wiggy's. The Woobie drapes really well and the warmth is surprising. For me, the warmth seems to come on instantly. It packs down easily to the size of a 2 liter bottle and then compresses even more lengthwise if you push down on it.
Is it better than the Wiggy's? Yes when it comes to weight and comfort factor. Price is a bit steep but compared to an Integral Designs poncho liner, it is actually less. You don't get the zipper or the head hole on the Woobie the way you do on the ID model, but then again, in summer weather, I just use it as a blanket anyway. It can tuck easily under a sleeping pad to trap more heat in and still wrap around your body. Paired with a closed foam pad, it is really warm.
Overall, it is a personal choice if the woobie is right for you. I get outdoors a lot with my job at the WLC and it is justifiable. For others, $120+ for a blanket might be ridiculous. Like I said, it is a personal choice. I wanted the best night's sleep possible and I went with the woobie.