Support response time, as quick as possible. My support staff manage a response within 15 minutes. On average it's about 5 mins to date. Sales is a couple hours as they are not 24/7 but still. I'm sure most will claim this as untrue, a long time ago I would agree as I had bad experience with providers. You're always welcome to try.
To have a reponse later than 3 hours I wouldn't accept. Your website could be down and 3 hours of downtime for many business can be very very costly. In my oppinion it's in the top three most important for a web host.