So apparently in the next update, the 23.5 one with the asteroid mission and new extra large parts, they're going to buff Ion Engines. And by buff I mean that their thrust will be 4 times what it is now, I'm guessing they're going to tone down their power usage per N of thrust as well.
You know what that means? Solar powered Ion Engine planes, ah but not the old solar powered ion engine lightweight drones of yesteryear. Manned solar planes for fucking Duna.
Also Munar Ion Engine hovercrafts should be possible since TWR>1 on the Mun is just barely possible with Ion Engine now. Oh and regular boring ion engine manned ships are more practical now.
They've also added flag decals to quite a lot of parts. So your space program flag will show up on the 3-man capsule, some of the new and old fuel tanks and other stuff. It wasn't outright said that shit is in now, but if the guy is officially streaming an experimental build I am assuming it has no mods and they added that functionality to the stock game.
You can also now timewarp from within the tracking station and the space center screen, although there's no in-game time clock on either of those. They need to add that one day.
Also we're getting new bigger boosters, two new extra large engines (one has a vacuum ISP of 380), extra large fuel tanks, an escape tower part the size of a large parachute cap, the claw (lets you "dock" with anything without a docking port and even allows you to transfer fuel, so a space rape enabling mechanical penis really).
The randomly generated asteroids look pretty cool. They come in sizes from A to E, where the E ones are the most massive with something like 3000+ tons in mass IIRC. Good lucking moving that shit. Best part is that you can use the claw not just to move them around, but also to attach small modules to its surface and build a space station around the damn rock and it treats everything as one vessel. So you can have Ork Roks in Kerbal basically after you attach enough fuel tanks and engines to one.
Missions and other new career mode mechanics are coming in 0.24 as planned. Probably another month or two before they release that.
Also manuever nodes now have precise control, and you can now tweak RGB color setting on the electric light parts so that they give off light in any color you desire.