Very much against it. It was at its root a pagan celebration of the dead. The druids carved out pumpkins and called for demons to inhabit them and went around door to door demanding people give them items. Those who didn't comply were sacrificed on 'bone fires' this is where the traditions of pumpkin carving, trick o treating and 'bonfires' come from. There is nothing even slightly Christian about it.
If I was American I would probably celebrate harvest instead. Some shops here and for sure the cities try and cash into Halloween but for most of the country, it's basically a fizzer. The whole pumpkin thing in the middle of spring planting doesn't jive. We have Easter in the Autumn/Fall and Christmas is in the middle of summer so our country has a completely different feel over these holidays compared to the US.