If you value your time more than your money, then they're an excellent service that gives you a new suite of capabilities for making that tradeoff. They have been able to arrange everything I've asked them to do. What I like about them is that I can make a request without having any idea how to go about getting it fulfilled, and Magic will figure out how - they'll do the research and find a solution. They are familiar with service providers for all sorts of unusual tasks and will set them up for you: personal chefs, car servicing pickup, garbage pickup - for everything I've asked they've had an answer.
They are primarily limited however by their staff on the ground or lack thereof. Although they've been able to organize couriers in several cities to accomplish tasks, they have occasionally been unable to find couriers on the day of a request. Magic is a generalist service: they can do virtually anything, but not necessarily within the same hour you ask. They're worse than specialist services like Postmates at tasks like basic food pickup and delivery (mostly due to lower availability of couriers). Magic is most useful when your need is unusual and a typical service won't be able to get it done - or when you want a complex problem to be solved and don't want to have to think about or manage the solution. At such a task, they excel, and they've always come through for me in the end.
The Magic staff are very friendly and personable, as well. Their customer service is a tier above any other company I've interacted with. They handle requests with unusually high intellectual and emotional intelligence, and care. (Disclaimer: I haven't used Magic+, only the original Magic which has been surprisingly cheap for the value it adds.)