Pros
The product team is great and is led by someone who knows what he's doing and does a great job overseeing the team. If you're an engineer looking to join a small, high-velocity team, Groove will be a great option for you.
Cons
Groove built its reputation as a company that "shared everything" on its blog—the real numbers, processes, "behind the scenes" stuff. So you know, none of that is real. It's all made up to catch the attention of the entrepreneur/wantrepreneur market. The revenue, subscriber, and user numbers reported on the website and mentioned often in the blog by the founder are all made up numbers that are FAR above the reality of the company's actual position. If you care about ethics or honesty or transparency, Groove looks like a great place to work from the outside looking in, but that is a mirage. What you see in the articles and on the website has very little relation to what actually happens behind the scenes. The company is not growing, and it's not operating at scale. It's also not a good place to work as a marketer in general, since there is no coherent strategy and no one in charge of the team. You just have to make it up as you go with minimal guidance from leadership.