That said, Tictail is currently a free service. From what I can tell, no-one's paid them a penny. The real test will be how many of their merchants stick around once the add-on pricing is (a) announced and (b) goes into effect in May.
EDIT: From their help section (http://help.tictail.com/customer/portal/articles/531368-how-...):
> Our ambition is to offer these add-ons at between 1€ - 5€ / month.
(full disclosure: I'm a Shopify employee.)