I could honestly say, having read particularly negative reviews about their interview process, the interview with Meltwater was not bad at all. I actually had had fun! Meltwater staff make sure you are comfortable at all stages throughout the interview (they engage and check-in with your personally, provide sustenance, and possible giveaways). More importantly, they constantly solicit feedback about the interview process, which means they care about the candidate experience and your impression of them once you leave, job offer or not.
I felt compelled to write a note on here (when I don't normally do this) because I realize it may be those who did not do well or do not thrive in that interview environment and therefore have a negative experience who end up writing negative reviews about a company that, I believe, is just trying to identify the right candidate. They're interview approach helps them to achieve this.
My advice would be: Be prepared to speak in public and to present in front of fellow peers and the interview panel on topics you may not know much about. Be prepared to show your people skills because it is part of their culture and the position requires it. Overall, be confident in yourself - They want you to be the candidate they are looking for, you just need to see it in yourself first.