chip, everyone has their own interpretation of "useful" I guess. Personally I find it useful, but I'm fully aware of the limitations and with the scale modifications I've done in making the display myself I know how it behaves in relation to the sensor, so maybe a little more useful than something off the shelf. I agree in most cases a commercial unit chucked in a car and hooked up to any old sensor won't be much better than disco lights, except in some specific situations. I use the FPR pipe as an example that "hopefully" most people will understand.
If you want something that approaches what a wideband does, or the display has any form of AFR indication on it othere than 14.7:1 then your just kidding yourself..