It depends really how much you want to shell out for these discs. A rule of thumb for me, unless you've got an brand which is known to sell B-Grade or crap media, then that is where the problem is but if you have an alright brand, no worries.
I recently bought a pack of 50 Memorex CD-Rs from Amazon for Â£5.85 with free delivery (Which works works out about 11p / 12p per disc). The media dye is an MBI type, and not the CMC MAG I expected, which apparently according to members of Club MyCE has a very solid reputation for delivering solid bargain media.
Although I'm still a bit skeptical about their DVD media, since the recording pits are smaller and more likely to fail compared to their CD-R media, Memorex CD-Rs are very solid and production for optical media has got better, so problems for fading and unreadable discs seem to be non existant anymore than if you compare it to 10, or even ago.
They are great everyday discs and for data backups. Probably from the MBI code, burning tends to be rated slightly higher than CMC Mag code :S