I own the SU16F and have shot it on the past two weekends.. about 300 rounds through it. I can only provide a newbie's pov, though.
Cons
-- plastic default mags are garbage. So yes, use the LARs or any other metal mags. I broke one. Kel-Tec is shipping me out a replacement.
-- the bipod that is hidden in the foregrip is a pure gimmick. You wouldn't want to cut a steak with your swiss army knife either but at least you have a blade if you need one. Me, I am looking forward to replacing the foregrip altogether.
-- when deploying the bipod obviously barrel is exposed and you do not want to touch it, brush it
-- deploying the bipod is quite tricky. You have to press down on the two release buttons with the same amount of force or one 'wing' will deploy and you can't get the other one to deploy and you have to snap them shut again to try again
-- the spring that holds the bipod open is like an oversized paperclip and comes loose all the time and gets lost. I've since stored it away in a package of loose items as I never intend to use the bipod again.
-- I don't have any personal experience with semi autos besides shooting my friends' CZs and his SL8 and in my two weekend's worth of shooting I got a fair share of FTF and FTE with American Eagle 55gr FMJ. But others have reported none. I reserve my judgement until I've shot more.
-- I'm too much of a garbage shot right now to say anything about accuracy

-- no included sling attach points
-- safety is the push button kind located behind the trigger guard (different strokes)
-- it's begging for a muzzle brake. Climb on a fast second shot is noticeable
-- cannot clean bore from the chamber side even with complete breakdown. Have to clean it from the other side. Already broke an attachment on my cleaning rod trying to force a patch down it. I guess I should switch to boresnake.
-- pencil thin barrel
-- when proving safety you can't show chamber is empty by locking it open unless magazine is inserted. You
can do this without magazine you have to press the magazine indent (? whatever this is called at the feeding end at the bottom of the receiver) and pull back on the charging handle which then locks to show open. Not really obvious and I don't believe it is in the manual.
-- the hitch pin that locks the folding stock open has to be removed by poking it out from the other side with a tool like a pen or the pointy end of the cartridge. Others have already replaced it with a hitch pin that has a ring.
Pros
-- extremely light.
-- no complaints about the trigger
-- recoil very manageable.
-- I've cleaned it after each shoot and no real noticeable gunk .. Patches come back pretty clean
-- aforementioned gimmick bipod
-- the plastic foregrip and the stock are actually not bad. It's not top quality plastic and it's going to get marked up but it feels okay. The foregrip does heat up noticeably with each shot but not too hot that I felt the need to wear gloves (but wise to do so because of the exposed barrel).
-- can replace stock and foregrip with a railed foregrip and AR-style extending stock and pistol grip
-- short picatinny top rail included
-- Zytel receiver material seems pretty solid but will eventually get marked up
-- can store garbage 5 rnd plastic mags in the stock for emergency backup
-- iron sights with ghost ring shoot pretty well.
-- Kel-Tec seems pretty responsive to problems. I emailed them about my broken mag and two days later they agreed to ship me out a replacement.