I just starts using CustomerSure for Ledgerscope and Movemybooks and I am really impressed so far.
Sign-up and setup were quick and easy with options to add your own logo and use your corporate colours on the public-facing pages that CustomerSure creates for you.
Regarding Xero integration, the way is works is that you choose or create a post-invoice survey that you would like to send to your customers. CustomerSure checks every 15 minutes for invoices you have sent (or invoices created and paid on the same day) and then logs a survey for that customer. The survey is emailed out at a specific number of days after the invoice date - a delay you can decide.
So far, I think CustomerSure has given us a big-company looking customer support presence and the automatic gathering of feedback on a regular and consistent basis is going to give us insight into how our customers see us.
I recommend you give it a go!