It depends on what kind of Memorex media you use. If you get the "Wal-mart special" then you might have bad results. I know on the 650Meg gold one that I have used in the past has had the top peel off, making the cd worthless, the 700Meg one that I've used from a spindle has been touch and go. I had a good spindle and then I had a bad spindle where several of the cds were bad so I took the rest of them back.
I've had cd's that have worked fine from Memorex and now they don't, even though there are no scratches and other cds work in the same drive fine. If you have problems with Memorex, I would suggest using other more reliable cdrs like Fugi, TDK, IBM, Kodak, Verbatum, or Maxell. If it's important, use a better cd brand, if you don't care about the data and just want some cheap cdr media, then get whatever you can find for the best deal.