I have a gen1 and previously had a gen2. My gen1 started as a state compliant model; pinned (fixed) stock, non-threaded barrel, Mossy Oak pattern with a quad rail. I bought it used at a pawn shop. I eventually bought a new gen2 model with a threaded barrel and the m-lok handguard. The gen2 model had an issue extracting empty cases, which a new extractor fixed (Tandemkross or Volquartsen, can't remember which one). I did the Tacticool22 handguard upgrade and played around with both rifles for a while. Eventually settling on keeping the gen1 model with the threaded barrel from the gen2 and sold the other rifle to a friend.
The T22 handguard upgrade was well worth the money. The factory handguard uses a very small barrel nut and the handguard flexes a lot. The T22 handguard uses a huge barrel nut and gives the handguard a nice firm feel, like what you would see from a quality AR-15 free floated handguard. To swap handguards you'll need the barrel nut wrench (long tube with notches) and a way to clamp the barrel securely in a vise (non marring jaws of some kind).
Accuracy wise, you can do trigger upgrades like a regular AR (pretty sure I ran a Larue 2-stage at one point), although I eventually found the factory triggers to be fairly decent after they break in a little and smooth out. Barrel options are limited to Volquartsen, they run over $300 last I knew, and I don't know what kind of accuracy increase they would offer. I was not into match ammo at the time and am a significantly better shooter now, but both of my barrels seemed to like CCI SV for non-match ammo (I tested quite a bit of ammo at the time) and averaged in the 2-3 moa range. Last time I put the rifle on paper for groups was 2.5 years ago and over the course of 33 groups at 5-shots each, it averaged 1.2" at 50 yards with CCI SV off a bench with bags and I believe a Hawke 3-9x40 scope. The rifle is inherently lightweight, so benchrest precision shooting probably isn't what it's geared towards.
The rifle accepts mil-spec collapsible AR stocks. I've had BCM, B5, Magpul, etc. Some fit tighter and some fit looser, no surprise there.
Fast forward to today and the 15-22 is painted purple, wears some BCM & Magpul furniture and has a Romeo5 red dot. This is and always has been my daughter's rifle, but of course Dad just had to tinker with it. I've since switched to Tippmann for an AR precision "trainer" rifle and currently getting around 1.5 moa from that rifle with CCI SV and a Harrell Tuner. But maybe I should put a scope on the 15-22 again and see what match ammo will do in it?
Here are some random pictures over time, not necessarily in any certain order:
This is the current setup in all its purple glory.