One bit I always liked is that, unlike most scifi, in the CoDoVerse, most "habitable" planets are complete shitholes. Too cold, too dry, too hot, weird weather, high/low gravity, etc. Haven, Tanith, Churchill, Fulson's World, etc. All shitty. The "Earth-equivalent"/garden worlds are few and far between (Sparta, Xanadu, Friedland, etc)....and were largely spoken for (Sparta's pretty much the only one that had to deal with BuReloc, and that was mostly Bronson's doing).
The odds of any real-life "Earthlike" planet (roughly Earth-size/mass, in the liquid water zone, etc) having an environment comfortable for homo sapiens is pretty remote. Imagine trying to colonize a planet that's got a weird axial tilt....and constant 150kph winds.
The cute part about Tanith is that Pournelle flipped the script. It's a swamp/jungle planet, so classic scifi would have it as more primitive than Earth.....but it's the opposite. Tanith is a much older ecology than Earth, and the flora and fauna have a much more evolved set of tricks.....so most Earth plants and animals can't survive there (the local stuff outcompetes them).