A concealed carry holster needs to meet four criteria. It should (1) allow you to carry the weapon safely; (2) conceal the weapon; (3) allow for ease of access; and (4) be comfortable. I've now used the SmartCarry holster with my P938 50-75 times. Based on that experience, here are my impressions.
Safety: A+. The holster protects the trigger and never has it once disturbed the thumb safety. I always carry with a round in the chamber, with complete confidence.
Concealment: A-. If you wear a jacket or sweater, you'll have almost complete concealment. If not, there is some printing. The printing does not scream "gun!," but it could lead to uncomfortable questions. I don't think that anyone has been suspicious of me. But then again, I wouldn't necessarily know. Also, the weapon rides up, which tends to happen when you sit, which increases the printing.
Ease of access: B+. I'm grading on a curve. If you want complete access, open carry. Concealed carry is all about trade offs, and one of the trade offs with SmartCarry is that it takes a few seconds to draw. Still, I don't think that the SmartCarry compares unfavorably to pocket carry. Once can be faster than the other depending on what you're wearing and how you're standing or seated. Also, ease of access depends partly on your common sense. Wearing suspenders or a looser belt helps.
Comfort: B+. This is toughest aspect to grade. I typically carry for 10-11 hours at a time. I've found that, once you know how to position the holster, and you wear the right clothes, SmartCarry can be quite comfortable. Not as comfortable as not carrying, but comfortable enough that I don't mind carrying for extended periods. With the wrong trousers, SmartCarry can be unpleasant. Also, you have to take into account your body type. I am of medium build. If I were overweight or small, SmartCarry might not work for me, at least not with this weapon. If I were larger, I might carry a larger weapon in my SmartCarry. As it is, the P938 is about the largest weapon I would use with this holster.
Finally, I should add that the holster has held up well so far, but it's too soon to evaluate its durability.
In sum, based on my experience, I commend using SmartCarry with the P938.