The GDL 39 and GDL 50/52/50R family are all dual-band receivers. They receive transmissions directly from other aircraft in both 1090ES or UAT. Therefore, they do not need ground stations to re-transmit traffic.
Not so. You'll only receive traffic that has ADS-B Out directly. The ground stations will give you traffic in your vicinity that is on radar only (ie, does not yet have ADS-B Out). IMO, without the ground transmission, you might as well not have a traffic display at all, lest it give you a false sense of security or draw your attention towards traffic that is less likely to cause a conflict than a target you aren't being shown.
Yes, I know that even with ground transmissions it's still possible for there to be traffic that doesn't show up, but it's far less likely, and it's possible to see whether you're in radar coverage by looking at your transponder. I'd rather see more traffic on screen, not less.
The weather may be missing or delayed, but I don't care for in-flight weather. I was flying VFR for a little while and I'm comfortable with using radio to obtain weather.
Wow... You must not fly long cross countries much? I do NOT miss the bad old days of being on Flight Following or IFR, hearing "Attention all aircraft, Convective SIGMET blah blah is available on HIWAS, Flight Watch, or Flight Service frequencies", asking to switch, calling Flight Watch, and being told that there's a storm centered 28 miles northeast of some VOR I never heard of.
In the 15 years from about 1998 to 2013, GA went from not really even having moving maps that were worth a crap, to having very nice color moving maps, in-flight traffic and weather. The improvement in situational awareness is almost hard to comprehend.
Isn’t it as simple as entering the config mode on the 335 and then selecting UAT-in or 1090-in and selecting “on”? Whether you use it or not, at least you have the option to catch WX in case you need it in a bind.
Weather is always being transmitted. It's getting traffic inside your own "puck" that requires the reconfiguration. And it is just one setting, marking that you have ADS-B In. The system won't transmit the traffic if it doesn't think you can receive it.