A simple tip from Alex Pankratov that applies to almost every aspect of designing a product:
Simply changing the email subject from "Email Confirmation" to "Please confirm your email address" increased the number of completed subscriptions from 51% to 82%.
37Signals have harped on about it before too. Copywriting is design.
And then, there's also the fact that new users will fall back on text before other visual cues, as pointed out by Jennifer Boriss. Text matters.