Strengths: Receives strong signal, Seamless functionality with compatible Garmin GPS's
Summary: I use the GXM 30 with a Zumo 550 on my motorcycle. It works well and the addition of NavTraffic makes the complete system awesome. Be aware that the GXM 30 is not just an antennae but a completely self contained XM receiver (Hence the large price and size). Your XM subscription is attached to the GXM-30 not the GPS head unit, so if you use the GPS unit in multiple vehicles you'll have to move the GXM-30 as well to receive XM and NavTraffic.