I owned a Tarptent and used it for a few trips before I sold it. The design wasn't very good in moderate to high winds, it's not waterproof and condensation can be an issue if you don't have good airflow - that combined with a down sleeping bag was an issue for me. It was very light/compact. If you can shelter your tent from wind and it doesn't rain a ton it's easy to use and easy to carry on a bike.
I ended up with a Big Agnes SL2 which I like a lot better for my needs. It can be guyed out effectively against high winds and handles constant torrential rain with aplomb. It's not as compact/light as a Tarptent, but having confidence in my shelter regardless of the conditions I encounter and being able to camp with the fly off when not needed was worth it for me.
My SL2 has been going strong for me for several years now seeing a lot of use and wear very well.
If I was starting again I'd look seriously at Big Agnes as well as the light weight MSR offerings.
BTW - the tarptent I tried was a Cloudburst not the Moment.
Thanks, it's helpful to hear from people who have used both. I think I am going to err on the side of caution and get the Big Agnes, since I am going to be living in this thing for over a year.