Although we all agree that in general
40K grimdark universe has improved a lot and has more in depth fluff mostly regarding alien races maybe there are some aspects of old dated/retconned fluff you may miss. To me for instance:
- The old concept of Marines being psychoscrubbed criminal scum trained and indocrtinated to be blown to bits in the most dangerous missions. In that times they were not as irreplaceable as they are now, being "just" super shock troops utterly merciless and barely controlable killers. Yeah...

It's not that I don't like current marine fluff; it's just I miss old one sometimes.
- That the Empy was like a semi comatose guy able to have some limited interaction with others. He was able to emit some edicts and was able to hold audiences with very important individuals at times. I like it more than the current flowerpot like version of Big Bob.
What about you? For those not so venerable like me

you may want post regarding 2nd Ed. also.