Bivy sacks

[pickupel]

Hey Ole,

I'm riding the Trans Am Bike Race this year too. I think the big problem in going with a down jacket + bivy sleep system will be temperatures in the Rockies in June. For example, the Breckenridge area has an average low of 32F (0C) in June - pretty cold to just have a down jacket for insulation. Even if you're set on going as fast and light as possible, you need to consider quality of sleep - a Western Mountaineering bag will only weigh a few hundred grams more than a down jacket, but will likely allow you to sleep well in colder conditions. Even on the Transcontinental last year, where day time temps were in excess of 120F, I was glad to have a bag at night.

Ed

[roadpacker]

i have the gogo ex;  its a really great little tent.  i didn't care about weight too much and it packs up as small as pretty much everything else.  the one i have is a mesh fabric with a rain fly; so it's a little heavier and bigger than the standard gogo; it is a little more prone to condensation than a tent, but not as bad as a bivy.  i can even change clothes in it or read which is a nice feature.  the weight listed seems pretty accurate.  there are some extra pieces and the compression sack that nemo gives with the gogo is too much, so i just put it in a sil-nylon sack.  i might go with something lighter, but after using the gogo it would be really hard to go with less headroom (for me).

I did not like this tent; I found that I could not sit up on my elbows in it, and I had a very hard time pitching it acceptably during rainstorms. I'm swapping to a single wall for convenience. Condensation was an issue although not horrible. Didn't use it in winter.

[danimal]

If you want an ultralight tent where you can get up on your elbows, or just sit bolt upright, check out the Six Moon Designs Skyscape series.  I have the Trekker, which is the middle price, middle weight option.  I can't say enough good about it.  Quite roomy for one, I can sit straight up and change clothes, bring gear inside, or under the vestibule.  25 ounces for the tent and 3.6 ounces for a pair of carbon poles.  Cuben and $$$$ saves 10 ounces off that.  I carry 3 stakes as well, with the foot end tied off to my bike.  Bug net almost all the way around for views when it's not raining.  Deploy the sides for rain.  There's a bunch of good tents, and as someone already said above, no single right answer.  But this one works great for me. 
http://sixmoondesigns.com/tents.html