Well, I went ahead and did something crazy today.
I edited /skins/skinname/customer/views/checkout/complete.tpl so I don't show the Payment Instructions for payment methods 1 or 2.
Since my credit card and paypal payment methods are payment_id 1 and 2, I changed the first line of the template to this:
{if $order_info.payment_id > 2}
and commented out the original line:
{* {if $order_info.payment_method.instructions} *}
Now the Payment Instructions don't show up when the customer has paid via cc or pp.
I also added an HTML block to the Order Landing Page that thanks the customer for the purchase and such…
I really never noticed how deficient the order landing page was until I was testing the new paypal script today that came out with v3.0.6