I have a 5 pack of 4X Memorex, and also a 5 pack of 12X High-Speed Memorex, both manufactured by InfoDisc.
The 4X seems to be decent quality, I cannot remember having issues with them, but haven't used them in years due to the slow writing speeds.
I think I'm down to two of the 12X discs however, it seems after a while the discs just "die", with the CDR drive not being able to do anything with them. When you can get them to work, they seem to work good.
I've had best luck (in regards to CDRW media) with CMC discs if you can believe that. I've got lots of philips 12X media which are CMC that are still going strong. I also have a few Smart and Friendly 4X CDRW's which are at least 6-7 years old, with no problems to speak of.
Liteon 52x32x52 Black