Helen Shaw in Vulture is mostly positive:
https://www.vulture.com/2022/04/theater-reviews-potus-and-mr-saturday-night.html
"So why did I enjoy it so much? When the show isn’t trying to be a musical, it puts Crystal up in front of us and has him do Buddy’s act. Crystal is the kind of entertainer whose blade never dulls. Occasionally it even shows a bit of Buddy’s old act, including a clip from the film. In the video, Crystal’s timing is perfect, a pirouette, a riot. What a master he was! What a master he is. They creative team can afford to show us Crystal in his heyday because he hasn’t changed his fundamentals. His high-pitch zany key, the gunfire patter, the Big Characters (your Miracle Max, for instance)—those have fallen away, but his grace is just getting finer and finer. Crystal delivers each punchline like a Ping-Pong player hitting short; he delicately tips the ball over the net. It’s a class he’s giving, and it’s one you should go see him teach in person: Cultivate ease when you are young, because it’s the one thing that won’t desert you when the rest of your gags are gone."