I bought and played RotS for a bit and gave up after I couldn't trigger the storyline; I've come back again just a few days ago after getting Legends.
Some of these are valid even to my experience with RotS.
The leaders give a nice personal touch to things although I find they don't seem to affect things too much except for the diplomats. Perhaps I haven't been paying enough attention though.
The AI still doesn't cope well with Teekans, my favourite race. =) Secure steel and polymer, then chuck out colony ships and grab everything. Watch your income and strategic value reach impossible heights.
Super-epic-empire-from-nothing starting conditions: 1400 stars, ring, 5 AIs, abundant colonies, highest tech cost, highest pirates, highest space creatures, lowest independents, independents cannot form new empires, no victory conditions (storylines still there)
Started pretty ok, did the standard micromanagement to secure a steel and polymer supply then did an initial colony expansion. Ran into Humans and Securans, relations cool but ok. Ran into Ancient Guardians, meh. Did not try to steal tech from them to avoid breaking game.
year 2790, Galaxy fully colonized, basically by me. Natural trade keeps the Boskarans and Dhayuts happy despite -30 covetousness; they refuse FTAs though. =( I send one agent to blow up their mining stations. I have ALL the wonders and maxed out the mining, trade and colony infrastructure (brown) techs. Trade sanctions with the dinos lifted and relations repaired with hefty bribes, eventually get FTA. Both world destroyers, both super weapons, all mine. Most of the debris fields are also mine. Never bothered to disassemble (too cheesy). Have 2 Korrabian spice, 1 zentabia fluid, 1 loros fruit, only uncontrolled-by-me superluxury source is the Ancient Guardians.
Year 2828 (now), Shakturi not turning up. Shields tech done, sensors done, lasers done, missiles done... what do I have to do to get them to turn up? Galaxy fully explored and colonized, I have literally *everything* despite having fought exactly zero wars. Reputation at Heroic, especially after I stopped bribing pirates (I didn't ask nor want them to attack, I just want them to leave me alone for a bit so I can colonize in their system).
My colonies are still growing happily, although everything in the initial colonization rush is at max pop. Net income at +9 million and still growing (albeit slowly), military and civilian spending has long ceased. Total military strength is something like ~100 cap. ships and 300-400 carriers. I set carriers to 20% and the AI is using size 550 carriers as patrol boats... it likes to put carriers patrolling gas stations for some reason.
I have 'adopted' a fleet, gave it the best admiral and watched it play whack-a-mole with the pirates. Heh, the giant superlaser beam is totally worth it... when it hits.
To spice things up, I used the game editor to spawn a silver mist on a Securan colony and watched it chew on a triple defense base / med. space port combo. It ate the planet shortly afterwards and grows to 1500hp!! I sent my adopted fleet (which was hanging around outside the system) to try whacking it; you know, looking for a fight.
Turns out, Silver Mist AI needs improvement. It likes to go after fighters for some reason and can't catch them. Turns out, when each fighter has about 20-50% chance to deal 1 damage, 350 fighters nukes the silver mist into nothingness in a bare few passes. Turns out, a fleet of 8 custom-built carriers (basically fighter bays and engines, +essentials) are pretty damned scary when microed. I didn't even get to test my superbeam vs silvermist.
In a hypothetical universe (save branch), I declare war on the dinos and the fleet of 8 carriers wipes their entire homeworld defense. Large spaceport gone in three passes! Microed to keep out of range and with the superbeam capital ship for escort (to blow up their reinforcement fleets)
Also, the AI mining / gas mining station distribution is very sub-optimal. Likes to build worthless things at start (seriously, the only thing you need at the start is steel and polymer, everything else is secondary), and focuses too much on your homeworld area in the exponential phase. If it would focus on getting steel and polymer to Sol after I colonized it, the 30-strong constructor fleet I built could have turned Sol into a forward colony-producing base. It's not like my homeworld needs the help when there are 20 sources of steel and polymer each within 1.5 sectors range. As it was, I was colonzing about 2 colonies per week so I was ok with it, but I did notice that high population colonies aren't prioritized for resources like they should be.
Perhaps that was why the AI lost all the colonization rushes. I micromanaged the mineral sources early on to have lots of steel and polymer to stamp out colony ships non-stop. The AI doesn't seem to do that. Even without the "all roads lead to Nabuu" effect, you can tell solely from the (lack of) size of the AI empires where my homeworld is.
I also miss the discipline of the previous versions. Ships like to do their own thing even when they have player orders. I can't figure out how to turn down the engagement range to zero; if I'm micromanaging a fleet, I do not want it gallivanting off to chase some pirate coming through. Waiting at the gas station is for a reason, even if beyond the comprehension of the AI...