Many of these low cost plugs are cloud only with no local API. So if the internet is out you can't control them, nor can you block them from communicating with their cloud servers, which makes it hard to protect them or yourself from being hacked. Worse if the company goes out of business their cloud servers will be shut down and you'll be stuck. You do need to be confident that company will keep your personal data safe and not exploit it nor purposely or inadvertently release it. Finally, check that they're certified for use in your country so that if there's a fire or some other damage that your insurance will cover it. Other than that they should be fine :).