I use it regularly, the last time was a few days ago, and yes it is still good. However, I would not advise you to buy high-value vouchers. This is the kind of thing that makes Amazon flag your account and suspend it. Their system is sometimes too strict
Bitrefill is cheaper regarding Amazon vouchers.

I don't have a specific preference between both, I alternate but what i like with bitrefill is the possibility to top up my account to use it later