I went to basic in 09, The night vision gen one I used I had to google, as I really never had to memorize any nvg designations. It was the pvs2 scope, used in night time training with live fire, however the scope was never attatched to anything, i just had to use it handheld. That was during a live fire training where I got to play with the m249 with tracer rounds shooting far off from where the other soldiers were, just for effects to make it feel more like a night time battlefield. Outside of basic I have seen them but not used them since, the national guard had them in storage and would sometimes inventory them, but even they only issued gen 2 and 3, which leads me to believe they were just sitting there on standby, or were meant to be turned in a long time before and never were.
On gen 2 i Had those in basic as well as active duty, the ones I had in basic were dimmer than gen 1, and would flicker nonstop, which was likely from wave after wave of recruits abusing that equipment with little time to repair them. Those same gen 2(I believe you called them pvs7) in active duty actually worked very well. To me the gen 3 is just a little clearer and brighter than gen 2, unless you count gen3+ which gets up to twice as bright as normal gen 2, however gen 2 is 20x brighter than gen one, which is what I call a massive leap.
This is not going into thermal vision much either, I had a thermal scope in afghanistan and thermal on a maxpro mrap, the mrap had the worst thermal I has ever used, while the scope I had was absolutely amazing, I loved playing around with it in the guard tower.