Along the same lines, I recently traded my old King transponder for a new
Garmin GTX330. In addition to nice features like pressure altitude readout,
count up, count down, flight timers and aural altitude alert, its main
advantage is the mode S traffic readout.

Coupled with a Garmin 430 or 530 it provides the locations of multiple
(transponder equipped) aircraft within a twelve mile radius. The information
includes relative altitude, flight vector, and potential conflicts. There
was an excellent review in Aviation Consumer within the last few months
about the system.

After a little use, it's simply amazing how much traffic out there I never
saw, even with a careful scan. Even after a traffic alert it was difficult
to pick up other aircraft even within a half mile or less. Flying an
approach in a busy class C it was also neat seeing planes getting vectored
onto the final approach course and watching the spacing.

Considering the installed cost with the trade of the old King transponder
was less than $3,200 this is one of the best safety investments around. For
those of us fortunate to already have a Garmin 430/530 the extra cost of the
new transponder was a small price to pay for the added security.