For the purpose of earning points, they're treated like cash/credit. But, there are restrictions and they can be a pain to use.

There is a limit of $1,000 in LE certs per stay that you can use. I have exceeded that limit in the past, and did so often. However, in recent years, the staff are becoming more aware of that limit. So, don't purchase more than what you can use for the stay.

The other thing to keep in mind, is don't wait until check-out to redeem them. The certificates only come in $100 denominations, so if you're applying 10 certificates to your stay, it may take them 30 minutes or so to redeem them on the LE website and apply them to your account. That's not good, if you're in a hurry to get going and get to the airport. I typically visit the front desk during a time when it's not too busy, in the middle of my stay, and just leave them for the staff to redeem at their convenience, and ask they send a copy of the room account up to the room later. Don't try it right at the beginning of the stay either, as you will need to have some charges already posted to your room account, since they won't redeem the certs and put your account into a credit position.