I have heard discussions about the various versions of Led Zeppelin CDs for so many years.
I have yet to find a complete list of the various releases and which issues are considered the best. Sometimes when buying from Amazon it is still possible to find various releases of the same CD from different sellers (new or used). It would be useful to know which ones to buy.
This lengthy Zep forum tread mentions a few interesting things: for example, apparently one old CD re-issue of Led Zeppelin IV has the stereo channels swapped! (and if you are thinking "so what?", please click here and don't come back)