A vision just flashed before my eyes, of my coworkers all charging their credit cards on their desks, next to the cell phone that is also perennially charging.
As far as I know, neither of those things are true.
Many merchants I swipe my own card and they never see it. A waitress may question it, but I have no reason to believe they won't accept it if it is validated by their card reader.
The website says the battery should last two years.
When I first moved to the UK, you should have seen the hassle I had to go through to pay with my Norwegian VISA debit card. Norwegian debit cards have a portion of them that looks like an ID card, with photo and birth date. While they did accept it in the end, several places thought I was trying to pay with my passport or ID card, despite the obvious VISA logo.
Given that, I'd very much hesitate to try to pay with something that clearly isn't the original card. (Of course, I won't be able to anyway, since I'm outside the US, and every single one of my cards these days are chip and pin cards)
Any merchant can easily refuse it. They won't know what it is ahead of time. And many merchants have systems where they have to pay a (much) higher fee for certain credit cards (cough AmEx). So, even though they could accept them with their plan, they purposely don't. They don't know what the heck this unbranded thing with no logos are, so they'll just tell you to use something else.
