I am still trying to process the 'left the battlefield' mechanic. It's growing on me.
Aether Swooper: solid common for my casual Blue/Green Energy deck. Also, tokens are great permanents to leave the battlefield.
Aetherwide Whale: Limited bomb and good for Commander. Maybe there's a Commander deck centered on Energy that will be good.
Baral, Chief of Compliance: reads like a strong card indeed. I wonder how well it plays with the worst plainswalker ever issued (and one I often think about making decks with because I want to live the dream of a good deck with Tibalt). You draw before you discard, and that's important in a positive way. This card reads really strong. I can build a many different types of decks around it, and not just mono-blue, or Blue/Red. There are plenty of instants and sorceries in the remaining colors that I would love to cast for one less mana. I must break this card.
Baral's Expertise: Great effect, but not as a five drop if the only effect was the second one. With the second effect, I can do a lot with this card. I can return my own three creatures and trigger three Enter-the-battlefield (ETB) effects. And then I can cast something good for four mana. There are many really good spells in all formats that I would like to cast with this card.
Bastion Inventor: Improvise is even better in the eternal formats. Collect mana rocks, tap them for Improvise, profit. Now I need to come up with a deck that can cast this for U.
Disallow: Yeah, that's a good counterspell. Counter a single activated or triggered ability can be really good in certain situations.
Dispersal Technician: good in Limited. It's a battlecruiser variant of Waterfront Bouncer (1U, Blue, Tap, Discard a card: Return target creature to its owner's hand.)
Hinterland Drake: It would have been much more interesting if it read "can only block artifact creatures." Limited.
Efficient Construction: that's a fun uncommon for sure. If you can cast some one drop artifacts, bounce them back to your hand, and cast them again, this can yield many tokens. This card has a deck with the five Moxen and Hurkyl's Recall in it's future.
Illusionist's Stratagem: Great complement to Ghostly Flicker. I want to play this card.
Ice Over: great in Limited, great period. Yeah... I am cycling through all the artifacts that could be enchanted this way, and the more of them that I go through in my mind, the more I like this card in all formats.
Mechanized Production: reads Mythic all-right. It reminds me of Rite of Replication (Kicker 5 (You may pay an additional 5 as you cast this spell.) Create a token that's a copy of target creature. If Rite of Replication was kicked, create five of those tokens instead.) I like it a lot. I am not sure if it can be a competitive deck in Standard and I am hoping that it isn't because I want to play it and not pay a lot to do so.
Leave in the Dust: An always kicked version of Into the Roil (1U Instant, Kicker 1Blue (You may pay an additional 1U as you cast this spell.) Return target nonland permanent to its owner's hand. If Into the Roil was kicked, draw a card.)
Negate: Welcome, old friend.
Metallic Rebuke: I am not sure if Improvise can be as broken as Delve, yet deep in my Jhonny heart, I so want it to be, and will try hard to make it so. In the correct deck, this is a one mana Mana Leak. I want to play this in the eternal formats, where I have a much larger selection of artifacts that can be tapped.
Reverse Engineer: Same as Metallic Rebuke. UU, Draw three cards: I must make this happen.
Quicksmith Spy: Ral Zarek +1 says hello. Another Johnny rare for my Johnny heart. I am giddy as a schoolgirl. Oh, and Ral Zarek brought his buddy, Clock of Omens. Now, that would be 12 cards at four mana and that's a terrible start for a mana curve. Now I have to think about what the right mix of these three cards is, and how to fill that mana curve correctly.
Salvage Scuttler: Great effect, but a little too heavy... not sure I can benefit from it at five mana.
Shielded Aether Thief: That is one awesome Johnny uncommon. I would enchant it with something like Eland Umbra (1W, Enchant creature Enchanted creature gets +0/+4. Totem armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.), or one of the Ordeals from Theros, or ... well, you get the picture.
Skyship Plunderer: another awesome Johnny uncommon. It can be a counter on ANY target permanent. Can it be a poison counter on a player? Can it be a loyalty counter on a planeswalker? I want to play this card in many decks.
Shipwreck's Moray: It earns a lot of energy, and that's good enough for me in Limited.
Take into Custody: aggressively costed, great to have in my opening hand.
Trophy Mage: There are many three mana artifacts that are awesome. Most are not in Standard, and that's OK. More Johnny awesomeness.
Wind-Kin Raiders: Will need lots of artifacts to save on the casting cost. It fits a Blue/Artifacts deck.
Whir of Invention: Another great Johnny rare. I need to figure out how hard it would be for X to be 6, and then I can cast Wurmcoil Engine with this.