If you're only interested in basic situational awareness a Garmin GPSmap 96 does just fine. Not sure I'm ready to accept the excuses for needing wx displays when flying VFR. Every plane I've flown had windows.
Of course, when I was taking training using a Loran was considered cheating...
You mean you learned in a plane with windows? Geez, googles and a scarf were good enough for my instructor
During PPL training, sure, leave the GPS in the flight bag and learn pilotage. And later on, continue to USE pilotage. But when you have your ticket and start going places on multi-day trips like Tarheel Pilot is, even if you are VFR only, a GPS with XM weather is a great tool.
Most of the weather download focus is on Nexrad displays and their use to avoid storm cells while IFR. Granted, that's a "killer app", but as you point out, a VFR pilot should be able at all times to stay clear of T-storms by looking out the windows.
But the XM weather has several other functions that are great for a VFR pilot. One is the satellite imagery overlay. It is not perfect, but does show areas of significant cloud cover. Not much use when you are on a short flight in the local area, but launch out from North Carolina for Arkansas and it is sure nice, an hour and a half into the flight, to see where the clouds are.
Another great app is the winds aloft function. I've found it to be quite accurate, and a great tool in picking the altitude with the best winds. Or, most of the time for me, the least BAD winds.
One of the simplest and least written about functions is airport weather reporting. Want to know what the weather is at your destination? Scroll to that airport with the cursor (or go to the flight plan page) and click on it and there is the current METAR and TAF. Or click on any airport that shows a "weather" flag on the screen. You can maintain constant awareness of how the actual weather is compared to the forecast you received before you launched. Are fronts moving faster than forecast? Slower? Is the weather at your destination improving or getting worse? You can track it all the way.
There's tons of other info, including SIGMETs and AIRMETs that VFR pilots need to know about.
All this allows the VFR pilot to make good weather decisions well BEFORE he or she sees bad stuff out the windshield. Instead of descending to "see if we can stay underneath this", the pilot can check the METARs and TAFs, look at the imagery, and pretty much KNOW if they can get through safely. They can then opt for diversions, coffee breaks or entirely new plans early on while there are more options.
VFR or IFR, knowing what the weather is "down the road" in near real time takes a lot of anxiety out of cross country flight, allows for better decision making and, I firmly believe, enhances safety.
Jay