Depends on how long I've been doing one or the other. If I've been riding fixed exclusively for months and get on my geared bike, it'll feel weird (for like the first few minutes, not the whole ride). But if I've been switching back and forth a lot, I don't really think about it much. I also have the other difference of clipless on my geared bike and toeclips/straps on the fixed. Time to start training for my annual summer century, so I'll be on the geared bike as much as fixed in the coming months and the switching won't be a big deal.