Pros
Essential is a small, tightly-knit family of people dedicated to doing great work for interesting clients. The people are friendly and helpful -- if guidance or assistance is needed, all you have to do is ask. Great company culture.
The diverse range of projects (all kinds of medical, consumer, and commercial products) keeps things interesting and your mind engaged.
Because of the small size of the company, each team member can provide significant impacts on their projects, if they have the initiative.
Cons
Since each person is often working on multiple projects (in different stages of the development process) at once, the work requires people who can multitask, keep the "big picture" for each project in view, and still focus on the important details. Some people aren't suited to this. (This is par-for-the-course for consulting firms, but different than most corporate jobs.)
Disciplines (research, design, engineering) are relatively "silo-ed", sometimes working in an independent / separated manner rather than collaborating cohesively throughout a project.
The industrial design team sometimes struggles with thinking through the manufacturability of their concepts, leading to frustratingly iterative debates with the engineering team.