Pros
First, you have to know, MoroSystems has three branches: Brno, Hradec Králové and Bratislava. What I am going to write pertains mostly to the Brno branch. It is still a single company, but you can find different projects and approaches in each of the branches.
For a junior, MoroSystems is a good place to start. You are going to feel welcome and cared for. The onboarding process is pretty neat.
It is also a great place to learn. The developers care about technology and try to follow trends. You can find a large and active React community and a solid background of Java. Juniors very often get seniors as mentors, if not, most projects are pretty up-to-date technology-wise.
If you want variety, you can switch projects each year or so. Or volunteer for a temporary loan on a different project.
You can easily get to courses and conferences, even as a junior.
Much can be said about company culture: Most of the employees are outgoing and they love to be together. There is hackathons, bord game evenings or just pub nights. Also a few events for moms and dads. You can find a lot of cyclists, board gamers, mountaineers and interesting people in general. Everybody seems cool and easygoing. You won't get yelled at.
The management seems to geniunely care about their employees. The try hard to make it the company they would like to work for as programmers (the CEOs and CTO started the company as programmers).
Cons
There is no rest for the seniors, since there is never enough of them. Most seniors get assigned on multiple projects (2 or 3), asked to help with presales, etc. Most teams are comprised mainly of juniors, who are quite capable (they have a very good hiring process), but pretty green. If you are very hardworking, you can make your mark, otherwise, you can get overwhelmed pretty easily.
The projects are varied, but generally not very interesting. It is common for the customer to care only about price and number of features, having no heed for UX or -- heaven forbid -- code quality. And MoroSystems aims to please the customer. So you can very easily get into the rut of churning out new features with mounting technical debt. Very few projects offer interesting technical problems. It might easily come to feel like a rat race, but that seems to be the highs and lows of custom development.
The company culture also has its downsides. For an outsider it might seem almost cult-like: Most employees genuinely feel a part of a single team. They really like working there, they are perfectly willing to put extra hours into things, do work-related things in their free time. It is not mandatory, though. Also, the company might seem a bit too sunny. Being angry or frustrated is a bit frowned upon, as everything is either fine or in the process of being solved.
As for compensation, the salary is below average for IT, but hey, it's still IT. There is only 4 weeks of vacation and the management constantly rebuffs advances for an additional week.
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As of 2019, the company is transforming. They are getting bigger, which necessitates more management. This means the top management are losing contact with the lower-tier employees, which used to be one of the great things about MoroSystems. The result is, they are starting to care more about the company business needs than they employee needs. They still care, but their care is often misplaced, as they do not ask questions. And they are starting to place business needs in front.
Also, senior technical people who are not managers (i.e. tech leads, architects, ...) are losing their part in decision process. Which is ... unfortunate ... considering the strongest part of the company used to be the technology.
Now, the good news is, the company management feel it, even if they might not realize it. They are making a genuine effort to keep the company spirit, even as the company grows a bit over their heads. They know they are not perfect and they are trying to get better. So it may yet go right or wrong. It will be interesting to see how it plays out.