Surprisingly good for an action game of it's time. The atmosphere and level design is really enjoyable, and overall it feels immersive in the same way that older RE games do. It's missing some key QoL changes from later games, but what's here is great. The little tricks like reflecting Phantom's fireball with your sword or jumping on Shadow's spikes are all great and I wish that sort of enemy design was more common in action games.
It's an early PS2 game so naturally it also has frustrating platforming sections and hilariously bad voice acting. You can see some of Hideki Kamiya's more frustrating designs here that are common in his games, like forced minigames that drag on for way too long.