If you have used commercial as well as OPENSTAX OER textbooks for calculus I would like to know about your experience. How would you compare the two? Were there any disadvantages to using OpenStax?
The exposition, originally written by Gil Strang, seems pretty good to me overall.
I found a mistake in parametric equations (end of Calc II, beginning of Calc III), which someone attempted to fix but didn't. (The wording changed from a few years ago, but is still wrong.) So their editors may not be careful enough.
Other teachers at my college have complained especially about the quality of the exercises in Calc II. But I had my students doing their homework in MyOpenMath (course ID: 149086, which you can use), so I'm not aware of the details of that.
For Calc I, I also use a few other OER resources on the side. I start with exploring the derivative (and do a deeper treatment of limits later). I use a lot from Active Calculus, by Matthew Boelkins, for the first few weeks. I also provide some homework from Dale Hoffman's Contemporary Calculus for those first few weeks. After that, we settle into the OpenStax textbook. (If you'd like more detail about the activities I use, feel free to contact me at the email listed on my profile.)