Good: Fun for plinking. You feel badass using the carry handle. Iron sights work well enough to hit a pumpkin at 200 yards.
Bad: Heavy, not very accurate, poor ergonomics, barrel flex issues, magazines are really expensive.
Buy one if you want a fun, powerful plinker. It's not ever going to be a good long range gun compared to modern stuff. Think of it like a m1 garand. Just enjoy it as is, don't bolt a bunch of tacticool crap on it.
Sadly, those build kits have mostly dried up.