Greetings,
Started with a 520 GoPhone, dropped it and broke the glass, but was able to repair it myself. My grandson has it now and uses it sparingly for games.
Got my wife a 520 which she dropped and broke. I could not repair this one and replaced it. She swears by her Incipio cases.
Purchased a used 925-a gorgeous phone but limited storage and weak battery motivated me to replace with a 640. The 925 is still used for games.
The 640 runs the inside version of Window 10! Very nice piece. Great battery life!
Updated my wife to a 640, which is still her daily driver; she has stayed with 8.1 (I bought a spare 640 GoPhone for her, as she hates change. It remains unopened.) The old "yellow" 520 still works well.
A new 650 dual sim was next as the 640 was limited by the 8GB on board storage. (The 640 works fine.) I love the feel of this phone.
My last is a 950 dual sim that I bought used. It runs the Insider Preview. It has a beautiful screen, is buttery smooth, plays nice with MicroSD cards, takes very nice pics. It could have a longer lasting battery.
To summarize, all of the phones except for one 520, continue to work well!!
520's-3
925
640's-3
650
950.