Definitely from birth - the Graco one that we had for DD had about 6 seat positions form fully reclined to stright up. She absolutely loved it and we only stopped using it when she got too big to squash her in! - which BTW was about 9-10 months so we got good use out of it.
We put her straight in it when we walked in the door from the hospital and then dh and I just stood there looking and each other in terror as if to say 'Oh my god...what do we do with her NOW??!!'lol
If it's any consolation mum2max we had a bouncy like yours as well and she loved that too!
It might be worth asking around to see if any family or friends ahve an electric one that you can 'borrow'. Dd's has really done the rounds over the last couple of years. It's been to quite a few friends houses for their newborns but it's the only 'baby' thing that i haven't been able to officially part with. I had wanted one for ages when I was pg but never seemed to have the spare money, then when dd was in NICU after her birth Dh turned up at the hospital with one, in exactly the right fabric and colour as well!
The instructions on my Graco one say from birth in the fully reclined position, but only for 30 minutes at a time. Hah! DD used to have a 2-hour nap in it, on high speed, every morning for about 4 months - the only way she would sleep in the day without me holding her. I used to feed her to sleep and then carefully sneak her into the swing, and quickly turn it on full speed.
Ds is rather more civilised about his sleep, so he goes in the swing when he is awake - its next to the dining table and he sits in it for mealtimes (he's 8 weeks so not joining in the meals yet). Total Godsend that swing, best purchase I made.