'Unscented' is always a dangerous claim to make, and it definitely is the case with Sure here; there's obviously no 'added' scent to it, like lavender or menthol or whatever else companies feel obliged to throw into deodorants nowadays, but there's a definite lingering odor that hangs around when you spray it, like 'new car odor'. This is probably the propellant or something, I'd say. Thankfully, the smell doesn't actually stick to you, and within half an hour, you can't really tell you're wearing it.
Effectiveness? It's hard to say, really. It certainly stops you sweating to some degree, but given that I live in the Midwest, and it's just coming into August, nothing short of laser ablation of the sweat glands would stop you sweating completely.