If you have a chance to get one, DO IT!
Good gun? YOU BETCHA! Fast gun? REALLY FAST! I found the light gun/heavy recoil INVIGORATING!
The SideSaddle for the Benelli works. SureFire makes a forend light, if you really wanted one. I modified a plastic heatshield for the 870 to fit; removed the sights and filled the rear dovetail with a blank, and installed MMC Ghost Ring sights with the winged front post.
If it was made before Sept. 13, 1994,(exact date of manufacture can probably be determined by the serial# and a call to Beretta) a Choate pistolgrip full stock can be installed. Choate made the stocks for Beretta, I'm 99% positive. Either that, or it's the best clone I've ever seen.
Check the letter code on the gun for year of manufacture. The Modern Beretta Firearms book by Gene Gangarosa Jr.has a list: page 282; recent codes are AP/1986; AS/'87; AT/'88; AU/'89; AZ/'90; BA/'91; BB/'92; BC/'93; BD/'94 --- after that, I don't have the info.
My 1201FPG3 has the "BC" stamped with the other proofmarks on the bottom in front of the triggerguard.
One other consideration in my choice was the fact that the safety button location behind the trigger is in the same spot as the Browning BAR, Remington 7400, 870, 597, etc. Familiarity counts under duress...
I hope you find this helpful.