We're considering the 'Business' package (we are a business).. However, we don't see value in the Business upgrade.
These are the added features over 'Personal'
-- Basic Add-Ons
-- 3 Sites
We don't need more than one site.
The only add-on of interest is the Mail-Chimp add-on.
Regarding MailChimp... what's the advantage of an add-on? Why wouldn't I simply add my MailChimp code into a plain form? You mention double-opt-in capability, but isn't that a function of the MailChimp service?
Also... we're strongly considering Jotform or Woofoo for these two features:
1) We need the ability to conditionally display form fields based on previous entries
2) We need the ability to store and display (graphically) survey data