I live in New England and have an '01 GS300. If you're in areas that get shoveled reasonably well (around the city areas) and don't have to deal with un-shoveled roads/driveways too much you should be okay with some snow tires. I made it through last winter without any but I really wouldn't recommend it and won't try it again this year. It's pretty easy to get stuck if you have to park in a snowed in parking space though (I had that several times in NYC).
Basically - a GS without snow tires won't be your friend if you're in 2 or more inches of snow in my opinion. Use snow mode on the ETC!
