If you want the features and ease-of-use of Dreamhost hosting but if every visitor is worth big money to you, consider Dreamhost PS or a dedicated server. No shared hosting service will be able to "guarantee" the service levels that you need.
I jumped at PS when it was offered for those sites I have where I'm paranoid about uptime and responsiveness.
I'll be a broken record here and say that my wife has been having problems with the filer on her shared server. Dreamhost has been very apologetic about it because it's been a chronic problem for at least two or three weeks.
She stays on here because it will eventually be fixed and she's comfortable with being able to set up and manage her site using the panel. (She can also call upon me to help on those rare occasions when she needs to shell into her account)
Use the [color=#CC0000]3DOM50[/color] promo code for 3 extra lifetime domains and $50 off
More Dreamhost coupons here!