Very good topic. My personal experience:

Cassette tapes. I have about 200 of 'em half that have personal meaning to me, some as old as 30 years. No more than 5% are giving me problems, and several of them are because TDK made a C-180 that was so thin you could see through it! Try splicing that mama!

I'm playing the cassettes into my computer doing a 16 bit Analog to Digital and recording to my hard drive via Cool Edit. Mostly happy with the results. I've been able to do this with LPs and take out skips, which is fun.

Some CDR's are obviously cheap. CompUSA store brands have the reflective layer on the outside of the top of the CD. They are worse than worthless. If you write on the CD or scratch that surface you can lose the playability of the entire CD.

I recently tried out a Philips audio CD recorder. Reason was it purported to be a time saver, allowing you to play an LP into the machine which would immediately burn to CD and interpret the record bands as unique CD tracks. This saves a ton of time over playing the LP into a computer, then utilizing an editing program to locate, separate, and name all the tracks.

Unfortunately the Philips FW-R33 doesn't correctly identify the LP tracks. It also only uses 'audio CDRs' which are more expensive than basic data CDRs which computers can use. When I called the Philips help line, they blamed the brand of CDR media I was using, and told me not to use certain other brands. This would have been helpful if they had printed it in big letters on the box, because they are the most available and least expensive brands in my area.

My solution is to go back to data CDs and the more laborious computer treatment. And to leave much of my archived music on a large hard drive, duplicated on another large hard drive, and to have one of those drives on a computer which never goes online (to avoid viruses, worms, and bacteria).