There have been two playtest documents, one on races, backgrounds, and level 1 feats, and the second on the Expert classes (rogue, ranger and bard) plus more feats (mostly level 4 with some level 1). Both have also included a Rules Glossary that has tried various things, like changes to crits and exhaustion.
They have said that this isn't a "here's the rules we like and we're going to be iterating towards better", but at times they will be throwing a lot of different things out to check how they work, a bit like A/B testing. For example in playtest 1 they gave out Inspiration (now called Heroic Inspiration) on any 20 rolled. In playtest 2 they changed that to on any 1 rolled. Just trying to get feedback.
So far it looks like a 3.0 to 3.5 shift to me personally - that they will end up tweaking a whole bunch of small things but leave the bones mostly in place. Enough to have to republish everything but not enough to feel like a shift to a whole new editions with new paradigms like 3.5ed -> 4e or 4e -> 5e.
@Yora if your problems with 5e have been in the details, this may very well solve them. If they are more foundational this will likely not address them.
But it definitely will be changing. Backgrounds right now have become the freeform bonus granters (ability score, skills, feat, etc.) Races with less need to carry those have lost subraces as a mechanic. Both ranger and bard aren't spells known classes, instead having preparing from the whole list a larger number of spells, but pre-defiied what level those spells are. Videos have said that is going to all spellcasters.
Many of the changes of the more recent 5e books don't seem to be replicated in the playtests. Changes to races in MP:MM, moving away from short rests, and the like aren't replicated in this. Like while I don't believe it actually true, it feels like these playtest documents could have been written in 2019 instead of 2022.