Very effective for root excavations, as well as a variety of other work. I have been on projects where it was used to trench through root zones for utilities, irrigation lines and drainage. To "till" in compost to ammend under trees for planting perennials. Bore holes for aeration, check for the prescence of living roots after construction or other disturbance. Excavate along foundations to check for roots prior to landscape and home renovations. Almost anything where dirt has to be moved or removed.
The drawback is the mess. On a single tree, or a few small trees you are almost better off doing the work carefully by hand. After you set up some containment, be it plywood or tarps, to help hold in the blown dirt, then cleanup, there are times when the old way is the best way. A great tool, but I wouldn't want to have to use it for every situation.
Neighborhood of $1100.00 US. The cost is in the nozzle. A specially designed venturi that creates a supersonic flow of air. Not easily duplicated in the DIY (Do IT Yourself) models, but I'm told that for $35.00 the DIY kicks butt. 185cfm, but there is a larger nozzle that needs greater flow. Check out the folks at Concept Engineering Group.
The Airspade seems to be all the rage here in Dallas. A few years ago, only one company had one. Now I know of five (probably a few I haven't heard about also), and everyone is talking about it. The company I work for is set to order one this next week.
I think the thing I like best is that it opens up another avenue of tree care that we have really been neglecting. In the Dallas area, most of the trees we care for are planted. Most are planted too deeply. After getting called out to "save" trees after its too late, it is nice to be able to do something proactive. Pruning, removals, sprays... Treating symptoms. Sure we can get down on hands and knees and scratch away the excess soil, but how any times do we really? Spend $1100.00 on the Airspade and $300.00 a week to rent a compressor and you can bet you'll sell some root collar excavations. You'll start looking at the base of the trees when you walk onto a property, and then look up, which really is what we should be doing most of the time anyway.
Louie Hampton