Me too. I definitely don't use Safari enough to justify the cost. But the instant access and the rational useful model make so much sense that I really don't mind.
Here's a little tip. Safari Books actually has a 5-slot $9.99/month plan but you can only see it if you are already a member. So just sign up for the free trial and then change your membership over to it. I guess they offer it to people who sign up but then think $28/month is too much.