Pros
Good for filling out your resume and getting publication experience.
Cons
Just feels so unprofessional. MXDWN is virtually no one's first source for news -- it's been around for over a decade and seemingly no one really knows about it. Do not expect to make good connections through writing for them.
The staff are very young, and they're nice but I got the impression that most of them are just kind of figuring out how to do their jobs. Communication is AWFUL -- all via email. Sometimes staff will not check their emails/reply to you for days on end, and forget about things you tell them.
As for the writing itself, it's practically all just paraphrasing existing articles. 9 out of 10 times I got asked to just use articles from bigger, more well-known websites like Pitchfork or NME as primary sources. Editors leave zero feedback on writing besides grammatical things, so I feel like I'm couldn't improve nor learn how to write better.
I could've look past all of this if I were getting paid, but I didn't. It's no wonder they have such a high turnover rate for writers, considering that they expect an insane amount of work from them for zero compensation.