I'm interested in purchasing a domain name for a new service I intend to market. I know that .com is instantly recognizable as a domain ending, and if I see stackoverflow.com I know it's a web address. However, I also recognize strings like github.io and mysite.tk as domains, since I've worked with domains like these.

To the average member of the public, if one sees an address ending in .io or similar, non-mainstream TLD (e.g. on a billboard or business card) would they immediately know it's a URL and to type it into a browser? Or are these new domains only useful 1) for a technical audience or 2) when you will be primarily promoting your site through links and not print?