These would be good in situations where power outages are the norm, for my edc light rechargeables all the way but i do keep stock of primaries as well and for the price per cell you can not really go wrong. I also used the ones from walmart and they lasted about two months of regular use in a RR before they had to be recycled.
I would not own a light that cannot take 4.2V. Primaries are for primates. :D