Well, salaries are typical for Barcelona and therefore low compared to what software engineers are getting paid in other places.
Even though they are working on their system of how someone can get promoted, it still has some downsides. In order to get promoted, you will have to achieve badges in which you have to proof your knowledge (through interviews, videos, demos etc.). It seems like an easy system to get promoted, but the amount of time you have to spend in your free time just to proof your knowledge can get quite high.
They only pay certificates if you do an AEM certificate first. AEM is, if you don't get deeply involved (which most don't), pretty boring.