A good transitional episode, though the main plot is kind of unengaging since we know we won't see Umezu again. But Kotoki Town isn't really all that special in the games, so I'll give them credit for putting those ruins there and making a story around 'em.
The opening scene where Haruka tries to capture Ruriri is hilarious. I love these early episodes where Haruka doesn't know a Poké Ball from a hole in the ground, as the dynamic between her and Satoshi is very well written. And this time, everything about the Rocket-dan's subplot is excellent - especially the visuals. It's funny seeing them all crammed into one phone booth (with the receiver pushed against Nyasu's eye when Sakaki hangs up on them), and I love their happy expressions when they pop up from the ground and shout "Tunnel completed!" only to find that they're not actually inside the building. But the biggest laugh I got was when they whisper the opening of their motto - and then Sonansu screams his part like usual and blows their cover, which is revealed to be crouching behind a rock no less than three feet away from the heroes. That's classic Rocket-dan stupidity right there.
The Magma-dan, despite what they'll end up being, is actually kind of intimidating in this one, even though I don't know why they're armed with Hellgar instead of Guraena. I'll admit, it really bugs me when the AG episodes depict Pokémon living in Hoenn that you can't actually catch there in Ruby and Sapphire. (I know the games don't equal the anime, but still...)