Pros
I worked full time at Micro-Leads for six months as part of a co-op program, and during my time there I worked on a little bit of everything, from product design and manufacture, to helping to set up new process equipment, and selecting materials that can be used safely in humans. The company rewards dedicated work and is willing to invest in its employees to help them grow and develop new skills.
In addition, the people are great. Because it's a small team (although they're growing) you get to know everyone, and even on days when I had to stay late to ensure a product would ship on-time I didn't mind because I got to have conversations with co-workers and work together to overcome interesting challenges.
There's also the fact that the work you do at Micro-Leads is helping to bring into being new methods of treating otherwise very difficult medical conditions. So the work is rewarding both due to the engaging nature of the challenges faced by in microscale manufacturing, and due to the end product being so impactful.
Cons
As with any startup, everyone always had a busy schedule. It's possible to thrive in such an environment, but it demands that you be regimented with your time and be capable of keeping your priorities in order. If you're inefficient with your time you'll probably find yourself working long hours to stay caught up. (I was usually able to stick close to 40/wk, although there were some weeks that went long). The startup work environment definitely isn't for everyone, but if you know you've done well at other startups, or suspect you would, then there are very few cons to working for Micro-Leads.