I don't know about "NEW" decking guns but there are semi-auto screw guns with extended handles for putting down flooring and the like without bending over, crawling on your knees, or doing the "Duck Walk." Never used them myself but have seen them. Seemed too high dollar for my limited useage. I paid under $200 for my screw gun with two batts, a charger, and a spiral saw thingy (about a hundred bucks separately) that uses the same batts.
Belt feed screws are more expensive than typical drywall screws but if you do much drywall at all and don't have a ready supply of trained helpers, the belt feed sure makes the work go easier. Maybe my reduced capability, advanced age, and lack of appropriate technique put me at a disadvantage that neccessitates my use of technology to compensate.
As I write this there is a track hoe with a 4 ft bucket and a D-6 Cat playing in the dirt around a pond just down slope of my house building site. The track hoe is $85/hr and the Dozer is $55 (with operators, no delivery charge) and I think it is a bargain. I'm not sure what they are doing that I could't do with my tractor for the most part B U T it would take me years and wear me and the tractor out. I feel that way about the screw gun too. I have a couple cordless drill drivers and the screw driving attachments to hold the screw while it gets started (real neat accessory) but the semi-auto is to the regular cordless as a semi-auto pistol is to a muzzle loading flintlock pistol. The muzzle loader will get the job done but not as quick and easy. (My particular muzzle loader is a 75 cal and is fun to shoot, just not practical for getting off very many rounds.)
Patrick