The key thing here is the possibility to monitor each individual plant and react to changes in its development or environment (in contrast to modern industrial agriculture, were things are done with huge monster tractors).
I'm sure it can/will be improved to serve more functions - like removing weeds and collecting pests without the need for herbicides or pesticides and so on.
Eventually, these will all become software problems which the global programmer community will be more than glad to tackle.
The most important thing about FarmBot and similar tech, though, is the potential to de-centralize agriculture again and make small-scale, local agriculture possible, without needing to employ human labor. Not only would this create a new market for high-tech agricultural tools and software and make growing your own food easy (even in the city !), it is a very welcome solution to the many environmental problems that large-scale industrial agriculture generates today.
So I'm very optimistic and happy about this tech and I wish you guys all the luck.