I started leveling an engineer and originally the idea of the kits felt cool, and was part of why I began leveling the class. The issue I have is that, well, they're extremely bland.
Most of the kits feel super one-note, with bland animations and effects. As mentioned by several folks, half of the kits literally use the same animation for every single thing they do. Heck, the bomb kit has no animation if you're running while using it. Add that on top of the poor feedback and effects on the core engineer weapons (Rifle much less so with the recent changes), and it feels necessary to use at least one kit, but also just not satisfying in the slightest.
From a mechanical standpoint I can understand how folks may enjoy pianoing through kits to get the best rotations, but I personally don't care about that as I'm admittedly a very casual player. I wouldn't mind learning if the skills were at least visually satisfying to use and half of them weren't just different variations of circular explosion. I wanted to have one of each profession, so I'm sitting here considering just dumping the level 80 boost I have from an expansion on it just to see if I have more fun using any of the elite specs (and to free up that shared inventory slot), as unfortunately its so far the one class I'm just not enjoying much.