So I started Scarlet last week, and I am very much enjoying this so far. I've just beaten Cortondo gym, and am now continuing my training before going for the Titan Klawf.
Thoughts so far: the region is lovely - a nice variety of landscapes, even in the early parts, and is great fun to explore, although it is easy to get lost in some places. Like in Sword, you can also get a wide variety of Pokémon early on - I have already have 100 registered in the pokédex - and raids do help with that. The threefold nature of the storyline is a nice idea, and I'm looking forward to continuing.
I've not done many picnics yet, but it seems like a good successor to camping.
The different arrangement of the menus is a bit strange, the pokédex not being accessed from the main menu especially, but nothing I can't get used to.
Tera Raids are interesting, as the battle system in them is different to anything else. (Whereas Max Raid in SwSh just run on 4v1 battle). Which leads me to the only real complaint I've had so far - they've managed to make the system for joining in raids online even more annoying than it was in Sword.