Just got my P3 a couple of days ago. We've had bad weather in Texas non-stop that I could only get in one short flight. I have played around with it inside the house mainly just testing the software and photo settings. Here are some things I've noticed.
-If you power off the P3 but leave your RC on along with the app, you are likely to get a bunch of error messages when you re-power the Phantom. I've gotten everything from IMU errors, bad MC connection, the Phantom and/or the camera needed to be upgraded (I already have 1.19 on it), etc. My fix has been to close the app on my iPhone completely and restarting it. Just restarting the P3 usually causes the same error. I hope DJI follows these postings as I think the app may still need a little tweaking.
-The compass was a little hard to calibrate. I ended up having to take off my watch and keys before it would take. I noticed the 1.19 firmware upgrade mentioned the compass calibration, so maybe that's fixed.
-Before taking off, take your time and make sure you have good GPS locks. Double check your camera settings. For some reason mine was on AE lock and a bunch of photos were pretty underexposed. Double check the failsafe altitude. I'm not sure why, but the iOS app keeps defaulting to zero. The first flight I kept it close and when I tried to land via failsafe, it landed where it was at and not at the home point. It could be operator error, but it never went up to altitude. The app crashed once in flight, and I got it back up by restarting. My guess is the altitude went back to zero.
-Based on the above, unless you're a real expert keep close and test everything. I don't think you have to stay in beginner mode as that's a bit restrictive. Find a large field, keep it in line of sight, and play around a lot. I know with just one battery and break in period, time is limited, but be patient with the drone.
-Don't panic if your app loses connection. I recommend everyone's advice to turn off wifi and bluetooth. From what I saw, you can close the app ( I would do a full close on iOS by double clicking the home button and swiping the app up to clear it from memory), and then restart it. It does make the connection pretty easy. Just remember that you may also have lost some settings. The P3 is so stable that just let it hover in place and wait for things to come back online. The RC is fully operable and for the most part you just lost line of sight.
-Invest in a Trackimo. It's a GPS locator that's very inexpensive, and when you get into distance flying, you have a backup to locate the P3 in case something happens. There's more info on other postings on the forum.
-If you fly in trees, or close to trees, buy prop guards. The best ones I've seen are from Bestem. Much better than the Summitlink.
-A great camera/gimbal guard is available from UAVBits. If you fly a lot, you will have some hard landings and this looks like it will do a great job. It's also a good platform to mount a Trackimo or other device.
-Like others have said on here and on Amazon, the Summitlink glare guard for iPhone 6 or 6 Plus that they show for a P3, does not work very well with the RC device holder. It is really for P2 Vision. You can wing it, but it doesn't accommodate the lightning cable and barely holds in place on the holder. You also have to have your iPhone out of a case.
-Make sure when you fly that you have a really good charge on your iPhone. The app and the connection goes through a lot of power. On an iPhone 6 Plus, if you're at 30% or less, my guess is that the phone will run out of juice.
-The second time I played with pictures and a movie, they didn't show in the app. Not sure what's up with that. I'm going to re-format the card. They do show on the card though, so not a huge deal, but again, that's what the app is supposed to do too, right?
-The pictures and video are beautiful. If you're a serious photographer, definitely go with the RAW and JPEG settings. You can make a lot of adjustments to a RAW photo in Lightroom. If you shoot the HDR or AE setting on the P3, you are likely to lose connection to the app. I have a 32GB High Speed Sandisk, and the file writing time seems to take away from the video data connection. Just be aware that it can happen. The P3 is so stable that you can probably do 3 manual exposure shots to get a wider range than the HDR setting and keep the picture pretty clean in HDR programs like Photomatrix.
Sorry to be long winded, but I'm hoping some of this can be helpful,