Pros
This is an awesome place to start your career. The pay is pretty good by journalism standards. You get a lot of freedom in what stories you want to write about, so even if your beat is X, if you are interested in topic Y, as long as it's an interesting story you can report on it. If you are proactive, you can easily network with people at The Wall Street Journal. They are also flexible about working arrangements (working from home, flexible hours) and vacation time.
Kontras
There is no emphasis placed on good management practices or manager training. Because of that, it's unclear how to get promoted or get any type of career growth. I've worked with managers who were uncommunicative and passive aggressive. Additionally, the managers have adopted an attitude of "everything's fine" without recognizing issues and working on how to fix them. They have failed to communicate any long-term vision for the site's growth. MarketWatch is a great place to start your career, but once you have the clips and work experience you want, the only way to advance your career is to take your clips and move somewhere else.