The Machinesmith is a fun class. Really all you need in a magi-tech artificer is right here and covers a lot of bases that I could think of and that I desired to play.
It does hit on a few pet peeves. It gains 'prototypes' of six levels that function like spells and it makes me have to explain why this class gets technology and others don't. Balance-wise it makes sense that a mechanic class only has technology that functions for itself the same way that a caster cant grant the ability to cast spells to someone else (wands and scrolls withstanding) but with Paizo's Technology guide it became easy to dismiss what the machinesmith does as personal magitech and leave it at that. There are some points in the font however where its hard to tell where a list of selectable options ends and a new class feature ends but that only required one double take. Also this class feels like it doesn't have a real place outside of campaign that uses high technology in general.
With my nitpicking out of the way, the class itself is balanced, fun and has a lot of options. Whatever you want out of an artificer this class has it. There are also some feats to support it, some archetypes a prestige class and spells that are also compatable with other spell lists.
If you got the print copy like I did you'll be surprised to see two extra goodies. There are the Fleshwraith and Host classes. The Fleshwraith is less machinesmith and more bioengineer. it seems to be missing it's hit die though but I assume it's a d8. The Host, also missing it's hit die, is a symbiote possessed class that gains eidolon evolutions as mutations from the creature living inside him.
Overall the product gives a lot of bang for the buck and the hit die and font problems aside it is my second favorite engineering class. Its easy to understand and varied in it's execution and a lot of fun to play so I'm giving it five stars.
[5 of 5 Stars!]