At 5$, the price is right. So I went ahead and bought it.
My initial impressions:
The lack of races isn't an issue, but they didn't add in anything to make up for it. Inverse World has Backgrounds and Grim World has something similar. I suggest using Grim World races with this supplement and either coming up with your own Backgrounds or shamelessly ripping them from Inverse World, though that's not necessary.
The classes aren't all that new, but 2Die10 Games has done a great job of making the classes feel much more steampunk. The flavor, like the looks and the names, are definitely an important part of any Dungeon World game. And they nailed it here. I'm also a big fan of the apothecary class, as someone who kinda has the healing touch of a cleric and kinda has the poisons of a thief. They also added some very good poisons that I'm probably going to use in my current dungeon world game.
The Biomechanical upgrades are great. I believe just these would be worth the 5$ alone. This is the main point of interest for this supplement. It adds a real value for gold that Dungeon World doesn't really have natively. This makes the motivation to seek out treasure strong enough that I feel this supplement is more loot heavy than base Dungeon World. There are also enough examples that it is easy enough to create your own biomechanical upgrades with appropriate cost values, as hacking and homebrew is a staple of all dungeon world style games.
The monster list is much more expansive than I expected, and they are all very well written. This is another section that would have been worth the 5$ alone. Number Appearing (another good monster manual style supplement for DW) provides only a bit more content than this monster section.
As for the moves. They added a lot of moves. Many of these are old moves with new names. It means that if you use this supplement with other dungeon world books then you have to figure out when one move has two different names and record or remember what the two names for that one move are. (2Die10 Games, please put in the names of the original moves in parentheses next to the updated moves for ease of use.) I would have also preferred if they had also renamed and tweaked the basic and special moves, since they did such a good job of flavoring all the other stuff from dungeon world.
Another note on moves. There are a few moves that don't fit the spirit of Dungeon World. Some take averages of attributes (where DW would just tell you to take the higher of the two). Some only have a certain number of uses per battle. First Aide gets rid of the need to make camp for heals, because it doesn't fail and has unlimited uses outside of combat. And then in battle it gets outpaced by Healing Salve, which is a very good touch "poison." Personally, I would edit it to do +1d8 health but require a roll against Wis with similar effects to cleric or wizard spellcasting. That said, these are all simple fixes to simple issues.
TL;DR This supplement is well worth the money for the value it provides. I think it could easily be worth 10-15$. Is it perfect? No. Why did I rate it 5 stars? Because I got plenty more than 5$ worth of content. I will probably be introducing Steam Punk elements into my game soon and be using many of these ideas, as I like them quite a lot. But, be prepared to do some tweaking if you plan on using this supplement.