This was a great experience. We stayed in the Willow Treehouse and it was absolutely wonderful. It poured down rain our first night and it was so nice and relaxing we didn't even mind getting soaked having to venture to the bathrooms. My one gripe though is that I wish the website made mention of how close the Willow/Juniper are to the main road because you could hear road traffic at all times of day. Not to an excessive or disturbing amount and never any honking or anything but it does take you out of the feeling of being in nature. Be aware though that the treehouse does rock with certain movements. I never felt unsafe at all but if that may bother you then be aware of that.
Oh, and most important tip for the treehouses: you access them via a rope bridge that is very bouncy. Just move quickly and straight down the middle or you'll start to rock and get a nice test of your balance/core strength lol. If you have a suitcase I'd suggest leaving it in the car and just bringing your clothes for the day in a small bag with you across to make your life easier. It's perfectly safe but that first trek across was definitely an experience in its own right.
The staff is very responsive via the direct line they give you but I think they're only around for regular business hours unless there's some emergency so be aware that if you have any issues, reach out to them ASAP because this isn't a major hotel brand with multiple staff members available at the drop of a hat. The first night we were there someone had left one of the shower doors open (despite the sign clear as day when you walk up stating to make sure they stay closed due to insects/snakes) and there was just a ton of dead wasps and several spiders in there. I texted the staff about it the next morning and it was cleaned up before we even went back to the bathrooms.
Also, I see a lot of reviews talking about the lack of things to do onsite or things not working. I can't speak much to that effect as my fiance and I came with the expectation of being in the treehouse at night and exploring the surrounding area during the day. There are tons of great parks around. I cannot suggest enough taking the detour to Round Mountain Distillery. The owner Mike is a great guy who is very passionate about his craft with great stories. Also, Angel's Icehouse is a great local spot with good food. If you're there on a Monday/Tuesday then you will probably end up eating there as a lot of other spots around are closed those days but that's alright because it's dang good with a wide variety of food/drink options. For breakfast, Guernica's Cafe is just up the road and has fantastic coffee as well as breakfast paninis. You've also got Marble Falls just a short drive away if you're looking to get in the river (unfortunately due to the years of droughts Lake Travis is completely dried up around the local parks).
Long story short, if you want a wilderness retreat that's unique, Cypress Valley is fantastic. Is it perfect and going to have the amenities/attentiveness of a 5 star hotel in a major metropolitan? No, there's a degree of self-sufficiency here. Is it going to be an experience that makes your friends and families jealous? You betcha.