When we did our garden last spring (first time at the new house) the in laws brought down their Mantis Tiller, they have a JD 5' for his 955 and the Mantis for the smaller stuff...At first I thought it was gonna be a joke of a tool, boy was I wrong...Dont let the size fool you, they work slicker then you know what...We ended up getting our own Mantis shortly thereafter.
Yes it takes a little longer in the spring & fall to till up the garden because its only 12" or so wide...BUT unlike a big tiller we use it ALL THE TIME. Use it all summer long tilling the weeds out of the alley ways. Use in the flower boxes around the house in the spring & fall...etc.
BTW...Our Garden is 25x40.
I have a Manis also that I use to loosen the soil around the plants, it works better than a hoe and a lot easier. It will get rid of grass also if you have any. The Manis is just a lot better than big tillers in between the rows, but I still think the world of my big rear tine tiller. Tractors and roto tillers are fine starting off, but during the rainy season, mine gets stuck and makes a terrible mess of my garden.