6Tag I find frustrating because it's very difficult to post a photo from camera roll or an album. Almost every time I pick the photo and it just resets to the camera. One in 50 attempts it actually holds onto the photo. Instagram is similar but it just crashes when trying to post a photo.
Interesting, I've returned to use the Lumia 650 and 640(bought it for wp8.1 upgraded to w10 since) also. I haven't used it Windows 10 for quite done time but find it to be really pleasant to use now. Amazon is a Web version based app without opening the actual browser, if you feel it needs improvement, leave feedback. Instagram has come a long way and as for Facebook, you have two choices now. Microsoft and Facebook have their own Facebook app so I'm sure you'll like whichever one.
Microsoft's FB app is no longer available. If you still have it installed it will work so long as you don't have the FB version installed. If you uninstall the MS version you cannot install it again. Just says not available for your device.
The Facebook version is utter garbage. Totally unusable. Crash, hang, slow slow slow, crash, crash, crash. It doesn't sync contacts, doesn't do live tiles, and doesn't do live video. Oddly the desktop app they have done is far better. Fairly reliable, live tile support and does live video. Quite nice to use on a tablet.
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