Memorex cd-rs are crap but cd-rw works great for me too. My rw's are old and all mest up and they still work.
I am sure that they are fine. What on earth do you need a 25 pack of cd-rw for. I mean they work good for your evox boot cd. They will work good for the few games that you can actually fit on a cd, but other than that they are still a cd and a dvd media will be required to do most of your backups.