Courtesy of James K., Virtually Green, San Francisco CA
The Mantis comes in two versions.
The electric is the far better choice if you have a power socket nearby. The gasoline version is noisy and not very powerful.
The torque on the electric is enormous. It easily can churn 10 inches deep through hard packed soil and has no problem spitting up large rocks. If you're using it heavily it may periodically trip its internal circuit breaker when it gets too hot: just wait a few minutes, hit the breaker reset button and resume tilling.
It's small and light enough to take on a bus carried over one shoulder. A guaranteed conversation starter.
Very sturdy. Have been using one now since 2009 and it's still going strong.
It's no substitute for a BCS for larger plots, but for small plots or rooftop use it's excellent.
Several other SPIN farmers weighed in favorably on the Mantis. Linda Borghi at Abundant Life Farm in Walker Valley NY love love loves hers.