I was undecided until I heard some clips on a page at NPR (National Public Radio) which showcased a few songs mono and stereo. Surprisingly, as I was contemplating getting the mono box, I preferred the stereo and thus am in the process of buying the stereo CDs individually - only the ones I want (Rubber Soul, Revolver, White Album, Abbey Road, Let It Be, for now). Best Buy has (nearly?) all stereo CDs individually on sale today for $12.xx and White Album for $16.xx.
Only did a cursory listen but Rubber Soul (stereo) has improved immensely over previous release(s).