I never had any issues with them. You can't expect a real accurate calibration, but it beat trying to find a tester to see if it was a new battery or kaput.
I tried rechargeables in the 90s and was not impressed. I hadn't realized they are better now. Will have to give them another go. These powercheck strips would still be very applicable to rechargeables too.
Linux mega supporter working from deep inside is now a super believable narrative.