First off, what Mac said is entirely true. It fits a little different than a similarly rated UQ. Just takes some experimenting to find out what works for you.
I have occasionally gotten condensation inside my Shamu. It isn't usually enough to wake me up; just enough to notice when packing up the next morning. I have found over the last two years and IDK maybe 24 nights in the Shamu that while IX is a good insulator it isn't the best thermal regulator. I think that because of it's light weight we expect it to perform like down, but down it is not. For me, it works works very best at varying degrees of venting between 50-70degF. With conscious effort to not over heat myself I can get to 40degF, but that is the source of the condensation I'm sure is over heating; for myself.
Other things I've learn...
Don't use an UQ protector, like dri ducks, or silny. The IX (even with scrim) doesn't soak up much water. I''ve found IX needs all the airflow it can get to better regulate tempurature. I even reccomend not having a full coveravge (to the ground) tarp; you need some airflow.