Unlike the others here, I know that it'll speed things up when used BUT the stuff has serious potential for very costly damage, especially in a Volvo where the parts ain't cheap.
I've seen a local turbo Volvo that has a NOS kit installed but I'd be afraid to use that in my turbo Volvo as the overboosted combustion chamber pressures are already high and I don't want to see my engine in pieces. The stuff is more likely to seriously damage your engine than your trans IMO.
Thec stuff isn't cheap either. I have a 150 NOS kit in my 'Stang with a 351 but those engines are tough and I'm only jetting it to 125 HP (considered "safe" by the Ford guys). I also only use it on rare occasions, just for fun and not often as the stuff kinda scares me too. It makes that 385 HP engine scary fast (over 500HP with the NOS shot). In a few shots, like getting onto freeway onramps the 10lb bottle is empty and it costs $47 to fill it again. You wouldn't want to use it often. Idealy, a turbo or supercharger is a better option as the added power is always there and it's safer. Adding either to a NA Volvo is not a good option however, way too costly.
Many people blow engines with N2O as they want to keep adding more and use it too often.