How do you feel about it? I was brought up with this and never thought anything of it as a child. By teenagerhood I no longer kissed my Dad on the lips (that was mutual. I think my dad didn't care for it, either). Too weird. My mom continued but I try to do the Latin kiss to her instead. She got the hint after a few months of it. Anyway, weirds me out for adult to adult, but I think it's an American subcultural thing.
Is it okay? Yes. There was nothing even closely sexual to it. It made me uncomfortable as I got older, but that was more due to my perceived reactions of strangers.
Do you do it? See above. I do kiss my 2 boys on the lips when we are at home. They are ages 5 and 3. Sometimes I kiss them on the lips in public. Depends on whether or not the people around me seem to not be phobic about it.
At what age (if any) do you stop? For me, I would say no later than early teenagerhood. Probably around 11-13. The kids will probably be uncomfortable with it first, but you never know.
How do you handle it if you were raised no and spouse was raised yes? That's not my situation. However, DH came from the "other side". I think that he thought it was weird and uncomfortable when my mom has kissed him on the lips! LOL- but I explained that it was just the way she was raised, etc. Anyway, she has really backed off since realizing that some people think it's weird. DH realized that it is NOT sexual in any way, shape, or form and is not so weirded out anymore.