Alright, here's my views in a nutshell.
The Capek update (1.8) changed a number of things, so even if you're NOT playing with the Utopia or Synthetic Dawn DLCs, the game's gonna be a little different. Notable changes include only needing a single governor for your core worlds, econ changes (ships got more expensive), alterations to the traditions tree, etc.
OK, on to Synthetic Dawn. I really like the way they've refluffed the traditions tree for a cybernetic race, as well as the various trait options (some of which obviously duplicate organic traits, others not so much). Machine races -generally- play a bit like hive minds do; they have the same gestalt consciousness and no-happiness traits. You'll be building power stations instead of farms to 'feed' your pops, though, and you'll have to manually build them rather than having them naturally grow.
Speaking of natural growth and whatnot, techs that would be appropriate for organics don't show up as options for machine civs. You won't see the Hydroponics Farm upgrades or Genetic Mapping tech pop in your research options.
Relations with other civs will be affected by their materialist/spiritualist ethos; materialists will like you more, spiritualists less.
I'll add more as I get to play more; I only got to play for a few hours last night! :)
