Hi Hawkman;
I have the M96 with both rifle and carbine barrels, and the top Picatinny rail. I like it a lot.
Compared to the AR 15, it's a bit heavy for a .223 at about 8 pounds, but it's very robust. Good accuracy (1.5-2.0" at 100 yards, scoped), at least plenty good enough for me, and doubtless others can do better. I can't really tell any accuracy difference between the two barrel lengths, but of course the 21" barrel gives more velocity than the 17.5", though the latter is more handy. Takes AR 15 magazines of any persuasion, but mine likes Thermolds best. Not anywhere near the accessories available for the M96 as for the AR 15, but I for one don't care, since I don't like to hang a lot of doodads on a military rifle.
Good military-style two stage trigger. Clean break, but little "break dawn" can be felt, so best to just pull steady. Good iron sight picture, uses A1-type rear sight protected by sheet metal fins, and a "winged" square front post which adjusts for elevation just like the A2, but unlike the A2 sight also adjusts for windage. The barrels are instantly removeable (5 seconds), and the modular design of the rifle makes it easy to disassemble for cleaning; everything assembles/comes apart with spring-loaded pins. (The BREN-style top-feed kit doesn't hold any real appeal for me, but is available for those who like to shoot from as low a position as possible.) The gas-operated system allows adjustment of the amount of gas used to cycle the action, a la the FAL.
Alex Robinson is starting to get the ball rolling on the equivalent design (based on the Stoner 62 instead of the Stoner 63) in .308, for those interested. Not sure how this will differ significantly from the FAL, except for modularity, but Robinson Armament makes really nice stuff, IMNSHO. The M96 ain't cheap, but it may be the best .223 rifle there is. (Standard disclaimer: no I don't work for them, own stock in the company, etc.) Best.