No, folks, they ARE NOT valid for first-class postage without a permit. I mail with old postage all the time. Ended up with a few of these stamps and presorted first class, as well, mixed in, which I used until I discovered from USPS they are not valid.
Spent time with USPS to get explanation. Can't use precancel first class without permit. Doesn't matter that you could when issued - you can't now.