R.,
I too thought my son was addicted to his swing. He slept in it up until 9 months, and as soon as the warm weather hit, he wanted to be flat on his back, touching nothing (or as little as possible :)
He may like sleeping upright after eating - what may not be a problem big enough for the Doc to fix might still be a comfort issue as far as reflux. I know my son has some, just not enough for the pediatrician to worry about. He preferred sleeping upright to laying down. I didn't even have to turn the swing on sometimes - just putting him in it was fine - although swinging generally eased his teething issues too.
Teething can start at any time, though generally they give you xmonths as a starting point. My son started teething at 3 months, didn't have anything to show for it until months later.
There is no problem with letting him in the swing, IMHO. Some people out there say 'it's best not to do it, he'll want it all the time'. Yes, this is true, but I think in 99.9% of the cases, they grow out of it.
Peace is important for my husband, so into the swing he went.
Good Luck!
M.