Currently browsing/typing this on L928 (635 & 710 lying right next to me). This was the best and most expensive phone I owned - I bought it from MS before Verizon even started selling them. The only limitation I had back in the time was I couldn't send text messages unless I switched it to 2G. Then finally, after the reset, I was unable to set it up for 4G internet (Verizon phone using w/ Tmobile). There was a guide for that setup with an international SIM card which didn't work anymore.
The final straw for me was that the apps started working/opening extremely slow. For example, I used WhatsApp the most (UC Browser 2nd) and it would take more than 30 seconds just to open.
As elky64 mentioned, as many others, my 710 was left behind with WP 7.5 (T-Mobile didn't release update to 7.8). Then I got 928, which Verizon after long delays finally updated to Denim. But MS refused to upgrade to WM10. I then got 925, and 635 later, both forced to WM10 then successfully downgraded because they were barely usable.
I always thought I won't buy any phone that didn't have a Glance screen, then after moving to Android I didnt miss it much. I never used Always On Display. I occasionally come back to these phones because I loved WP so much. But MS pushed people away from this system with their Coming Soon but never delivering strategy.
Remember MS was developing "a bridge" to port apps from Android to WP which they soon cancelled. When I said the same will happen with the iOS "bridge" people here didn't like it. But it never happened
Anyway, I must conclude this here. Sorry for bunch of mistakes you may see above