Hello AKDoc,
I've had my Remington 870 KEG 12 for a few weeks. I thought I wanted a Serbu, but had trouble finding one. The KEG 12 may be even better though -- I doubt you'll be disappointed with it. I don't know which is more enjoyable -- shooting it, or getting to show it off to family members and select friends.
After using the gun with the factory grip, I switched it out for the Hogue Tamer....better ergonomics and less felt recoil. I've used a variety of ammo so far, ranging from bird shot to buck shot. The gun is old school reliable with anything I've put through it. For pure fun, try Winchester's Low Recoil Low Noise Target Load. It's so mild, you can shoot boxes of it in one range session.
My gun is the 3 shot version with the 7.25" barrel -- 18" OAL. I found it just fits in the XXL scoped pistol case from AMS -- kinda fun to see a 12 gauge shotgun emerge from a zippered pistol rug. Also, Bore-Stores has a silicon treated gun storage product that's a nice fit for it -- their STC-2, which is 6"x23". It's actually designed for a scoped Thompson Contender, but the entire KEG 12 fits in it with a few inches to spare, including the pistol grip.
I hope you enjoy your KEG 12....they're a hoot to shoot!