I recently purchased the Rainbow. Although I can't make a direct comparison with the Lunar Solo because I don't own it and haven't seen it close up, I can tell you that I'm very happy with the Rainbow. Here's a copy of a post I made on the TLB lite weight site that offers some first impressions. I've editted the original post a bit to take into account further impressions as I got to try it out a bit more:
I received my new Rainbow a couple of weeks ago and just had an opportunity to set it up in the back yard over the week end and sleep in it last night. A few first impressions based on this limited experience:
First, I really, really like it! I've tried out the Cloudburst and older style Squall, and although they have much to recommend them, I always felt somewhat cramped by the relatively limited situp/head room. The Rainbow solves that problem for sure. I thought a one person tent might feel too enclosed and cramped, but that is not the case at all. It feels spacious, has lots of head room, and plenty of floor space. I also really like that fact that when I'm laying down, I don't feel that the tent wall is next to my face or virtually touching my bag at the foot end. The tent length and steep walls eliminate that feeling for me. Also, as Franco's photos show, there is plenty of floor space for gear to be stored inside of the tent at the ends and on the side.
Last night I slept in the tent with my dog, a Sheltie. There was plenty of room for both of us. Lo temp was predicted at about 28 degrees. The couple of times I checked a themometer inside the tent it was about 31 degrees. Outside there was a fairly strong wind(approx. 10 mph) when I first went to bed but it died down during the night. There were also light snow showers that left a dusting by the am. I slept with the vestibule completely closed and the upper vent closed as much as it can be, in part to see how the ventilation/condensation would be when it's battened down. Even in this configuration there is still plenty of netting around the periphery of the tent and the whole long wall with the door is netting. When I checked during the night and when I woke up in the morning there was absolutely no condensation. The inner walls of the tent were completely dry. To provide a more complete view of its ventilation and condensation, I'd need to try it more times in varied conditions, but as a first shot, it looks quite good from that perspective. I'm sure the initially strong wind helped, but it became pretty calm as the night went on, so it was still a reasonable test, I think. [I also slept in the tent a second night when the temp was about 20 degrees inside the tent with less wind and had essentially the same results--almost no condensation and very comfortable.]
The vestibule is relatively small, and I think would provide only limited space for gear storage, but it would probably fit a pair of boots, and maybe an empty pack laid on its side. As some of the photos show, it can be split down the middle and kept half open when rain is coming from one side or the other and could probably provide a limited shelter for cooking( with care). I found it a bit tricky to line up the 3 velcro patches to get it to close without any space where the two halves meet that could allow rain to get through. In fact, during the day it did rain and a bit of water seeped into one side of the tent. I think this happened because I didn't properly close the center closure in the vestibule. Later I figured out that it 's probably best to match the velcro strips when the vestibule is not pegged down and not under tension, then peg it down afterward. Once I did close the vestibule better, there was no more evidence of water. I need some more experience with the tent in rainy conditions to be sure that the vestibule really does prevent any rain from seeping through the point where the two halves come together.
The tent set up quite easily. I tried it with hiking poles first, then with pegs. With the pegs and the Delrin line tighteners on each corner that come wth the tent, it was possible to get a very nice, tight pitch with minimal effort. Using the hiking poles, it took a second time and some more study of the photos to figure out how to do it, but once I did, I saw that the tent pitches very nicely with the poles as well. I would suspect it's not quite as wind worthy with the poles, but still would be fine in most conditions.
The sewn in floor with the bathtub/flat options seems to work easily and well.
Overall I am really pleased with this tent. It set up quickly and easily. It immediately felt spacious and comfortable. The ventilation/condensation looks good. I'll try it out a few more times in the yard and write a follow up, but off of my initial impressions, it looks like a real winner!