Its good for building random things, but just like every other tool in the chest it has its uses and it has its limitations. I don't own one, but have used one when laying hardwood flooring and molding throughout a house. It is pretty fun as it just vibrates through the material
I just talked to my local hardware store about them this weekend. They told me that they have sold a lot of them and that they are good quality. Only had one of them come back. Plus they seem to come with a 2 year warranty, so I am thinking about getting one myself.
I am looking to use it on extruded foam board also. Typically, I use hot wire for intricate cuts; and use table saw for bigger cuts (or just snap off scored chucks). I am asking for the Rockwell Sonicrafter from Lowe's for Father's day -- unless it's at Home Depot and cheaper.