Scraps

They seem decent. It's basically annoying to face Scrap Dragon after Scrap Dragon after Scrap Dragon. Moreover, a late-game Scrap Dragon can basically win the duel, since it can destroy whatever hope you have left.

But, it's not exactly easy to get all of those Scrap Dragons out. Scrap Chimera and Scrap Golem are the usual suspects, but you can always tune Scrap Beast/Goblin to a Level 4/Level 5 non-Tuner.

In this way, Scrap Chimera is kind of like Black Salvo. Summon it for a free Synchro, but it requires the proper materials in your Graveyard. The difference is that Scrap Chimera is better overall, since you can go for more than just a Level 7, and also because it's easier to get Scrap Beast/Goblin into the Graveyard.

But still, they're both not all that great. Basing a whole deck around something like that makes it pretty vulnerable, since a bunch of different cards can counter a Scrap Chimera/Black Salvo/whatever play.

However, Scraps have the advantage of the draw/search card, Scrapstorm. It technically isn't a draw card, but when combined with Scrap Beast/Goblin, it's practically like searching another Scrap Monster from your deck.

So, Scrap, as a theme, is decent. It has potential, but not many people in the TCG have realized that potential. Maybe that'll change after the upcoming YCS in Toronto next weekend...