A few months ago I posted a way to get a Nemo GoGo down to 25oz by using a modified BD Ligtsabre pole (you can buy the pole separately from their website) instead of the airbeam. So you could save substantial weight this way vs. the Unishelter.
However, despite really liking the GoGo design, I have to agree that it is prone to condensation (thought I've never tried a Unishelter, just the ID eVent Micro Bivy and Chrysallis). I've come to the same conclusion as PJ that a bivy really should have the opening point toward one's feet so as to be able to exhale into the air instead of into the bivy.
Now, if the GoGo had a peak vent, it might be a totally different story. But despite the fact that the GoGo's vestibule is open around the edges, it does not provide the air circulation needed to expel the moisture from one's breath (I've considered rigging some sort of breathing tube to send all the moisture outside, but I can't imagine I'd get a good night's sleep breathing into a snorkel! I've also considered attaching a nylon DWR curtain over my chest to keep my exhaled air out of the sleeping bag area, but I haven't tried this yet).
Otherwise, I really like the GoGo's design concept. I am very interested in finding a bivy that I can just throw down and crawl into above treeline and not have to worry about a tarp being blown away or ripped apart, and the GoGo is the closest to that ideal for me due to the large vestibule, which means you can get in while it's raining and not open your bivy to the rain.
A side note about the fabric: the GoGo uses a 2-layer fabric, so the inside layer is an exposed membrane. This is how the GoGo can be lighter than the Unishelter using traditional poles. However, I find this exposed membrane feels wetter to the touch than the 2.5 layer eVent that ID uses. I think this is because the inner layer of the ID eVent is a woven mesh, so it keeps the membrane off one's skin/sleeping bag. This allows condensation to remain away from one's skin/sleeping bag while it exits the fabric. As a result, the eVent fabric feels much drier than the GoGo fabric. I've had the same experience with MLD's eVent gloves; they are only 2 layer eVent and feel clammy next to the skin, even though it is eVent. So when I wake up in the morning after using the GoGo, there is a thin layer of moisture on the surface of my sleeping bag, whereas the 2.5 layer eVent keeps the bag dry. This may of course have to do with other design factors, but I personally find the 2.5 layer eVent to feel drier to the touch than the GoGo fabric after a night of use.
Hope the above info helps the decision making. The following may or may not apply to your situation, but is a summary of the conclusions I've made about bivy use as it applies to my hiking style:
I've come to the conclusion that bivys are only good for an overnighter where you are above the bugs/heat/humidity (a.k.a. above timberline) and you are not expecting rain. Then it acts as a windbreak/emergency shelter, which is where I think a bivy really shines. But here in the PNW, where it can snow/rain and be very windy any month of the year (this past September I was on Mt. Hood with winds so bad I could barely stand upright), I need a shelter that will stay put and that I can move about in a bit more. I've chosen to try the new GoLite Shangri-La 1 as my bivy replacement. It's only 18oz, and is billed as a 4-season shelter. It has 2 peak vents, one at the foot and one in the awning. I own a GoLite Hex 3, and the Hex is the only lightweight tarp I own that I would trust above treeline. If the Shangri-La 1 proves to be as wind-stable and with similarly excellent reinforcements at the guyouts, then I may have found a bivy replacement. Sure, it's a bit more of a pain to setup, but it is lighter, will allow me to sit upright, should vent at least moderately well, and still provides 360 degree wind and rain protection. I could pair this with with an eVent overbag and only come out 4oz heavier than a Unishelter and have a totally bomb-proof setup. Or, I could pair it with a bug bivy in the summer and a Montbell UL Dry-Tec Breeze bivy (8.3oz) in the Spring/Fall/Winter for less weight and more versatility than a standalone Unishelter. Since the Motbell is waterproof, I could use that on nights where I'm not expecting rain, and if it does start to rain, my bag will be fully protected while I pitch the tarp. Sure, it's not as simple as a bivy, but it allows for more comfortable camping, and hopefully will encourage me to stop sooner and enjoy the evening rather than hike until I'm ready to collapse, since I can only stand 8 hours max in a stand-alone bivy.