Roku has just announced a pretty significant milestone: 5 million players sold.

Roku first launched in 2008, and the device was called “the Netflix player,” basically because its only function was streaming Netflix.

Over time, Roku broke out of the “Netflix box” moniker by adding plenty of other high-profile apps – Hulu Plus in 2010, HBO GO in 2011. Spotify and Time Warner Cable support more recently. As of now, Roku boasts around 750 channels. And with 5 million players sold, it’s clear that Roku holds a firm place in a market filled with streaming options. It’s about half of what Apple TV has sold (globally), for a competitive reference.

“What are people streaming on Roku? Tons of TV shows and movies. Netflix, Hulu Plus, Amazon Instant Video, Crackle, HBO GO and VUDU are all top favorites. Music is extremely popular, and consumers enjoy Pandora, VEVO and Spotify among other choices. News, sports, science and foreign languages from around the world are also big hits. Did I mention games? In 2011, we introduced casual games to the Roku platform with the debut of Angry Birds, which took the leap from mobile to TV for the first time. Angry Birds remains the most popular game on Roku today – by our count more than 3 billion bad piggies have been eliminated!” says Roku founder and CEO Anthony Wood.

Roku says that these 5 million boxes have streamed over 8 billion individual items of content of video and music, and that 25% of all Roku players stream over 35 hours per week.

Roku just launched their new device, the Roku 3 box, last month – and it’s been getting some good reviews. Are you a Roku user? What do you think the furutre holds for set-top boxes that pretty much exclusively stream online content to TVs?