As a baseline, I put in about 26 hours in the game back in February/March and was rather disappointed with the performance issues.
So, seven hours into the new 0.2 For Science! update and I'm very impressed. The game runs smooth as glass now, on the top graphics settings I'm getting a solid 60 fps. They really did their homework on this.
I've built a multistage rocket with eight solids and there is no stage wonkiness like there was before. I haven't used struts on my vehicles and I'll report back on how well that works. Meantime there have been no glitches at all in flight.
The Science part is much better that in KSP1. In the original game I struggled to earn science points to unlock stuff because I felt like the game was forcing me to go do missions I didn't really care about at that point, like IIRC aviation. In KSP2 there are primary missions that unlock further advancements in the science missions and also secondary missions which give science points but aren't mandatory. And I've found those secondary ones to be generally worthwhile, like one where I had to achieve an almost perfectly circular orbit of >99km but <101km.
There are four tiers of unlocks in the Research & Development area (IE parts) and I've earned enough science points to unlock the entire first tier without feeling like I'm grinding.
So my next primary science mission is landing on the Mun. It's doesn't have to be with Kerbals and the vehicle doesn't have to be recovered, just a soft enough landing so the probe survives.
I'll answer any questions folks might have and report back when I get further into the game.
. I'm burned out on Ready or Not, and waiting for the final hotfix before the holidays, so I'm going to play with KSP2 for awhile. I'm starting a campaign from scratch, doing all the tutorials, which are still just as cute 
. No early judgements yet except that I've done my first couple of flights at a solid 60 fps, so that's good.