You are correct. Garmin claims that with some upcoming changes the full
functionality of the data downlink will become available. Of course, we've
been waiting for WAAS and terrain for over two years now, with no firm
delivery in sight.

For me being a piston driver, base reflectivity is good enough. I also have
Stormscope and on board radar, and in combination feel comfortable with the
information provided. They each provide unique data, and when put together
give a good idea of the weather picture.

The downlink systems are really in their infancy, and it is obvious that the
manufacturers are struggling to keep up with the technology, particularly
with the ponderous bureaucratic certification process imposed by the FAA.
There is no "best" established technology.

I just don't care for a rat's nest of wires and cables in the cockpit from a
portable system (I'm looking forward to the bluetooth headsets as well), and
I enjoy the XM radio as well. So far, Garmin has always come through with
their products, although painfully slowly and well behind schedule.

Hopefully there will be an evolution to one standard that will be
inexpensive and readily available to all.