I've been looking at this card for a while and I was surprised nobody made a thread on it a month ago (and @hierarchnoble only made the thread after I mentioned it on Twitter )
I've had a list with this little guy in it since it was spoiled in the initial leak, and I've been waiting for the card to be released on MTGO. @cutlex covered most of the bases, but consider that the card is less problematic in multiples, and that multiple-Voltaic Key decks haven't been deeply explored. Me and @cutlex actually already had a Workshop list running 4 Key which this is potentially a deck-redefining card, so I'm not surprised to see his reply!
I think "cute" might even be underselling the interaction with Overseer, which I'm particularly jazzed for. If you play a turn 1 Steel Overseer and a turn 2 Voltaic Contstruct, you'll have a 3/5 blocker up for your opponent's turn two attack, assuming you have a pretty bad hand with these two cards and nothing else. That's not a particularly mind boggling effect on it's own, but we're talking about incidental synergy in a deck that already happens to run these cards.