I've used the ATD 200 on a few occaisions just to test it prior to panel mounting.  It does give a useful 'heads up', and makes you spot traffic that ATC didn't call.  One of it's shortcomings is
reporting multiple targets.  In that case, it may flip between one and the other forcing you to figure it out.  In that case I think my older model has the edge.  A row of LEDs are alot easier to see than
a changing digital readout.  I was condsidering the ATD 300, but unless I get a good offer on it, my 200 is fine.

    D. Story
    LNC2

Nice PA-30 for sale also.  ;-)