Reheated some in the microwave this afternoon--they came out good enough, but it was hard to get the outsides and middles to be a consistent temperature. Probably the oven or re-steaming them would have been better, but I was in a hurry.
Thanks for the compliments, everyone. I really was beaming with excitement while we were eating them because I've had several inedible disasters in the kitchen recently and I was feeling low on confidence. My next experiment will be
onigiri!