Most of the channels require you to have an account with the content provider. The Roku Player provides a unique code to link that account to the box, so you can access the content (video, audio, or photos) on your TV.
One of the best new channels, in our opinion, is Mediafly. The free channel aggregates podcasts--including all CNET audio and video content--allowing them to be accessed through your TV at the touch of a button.
In addition to podcasts, Mediafly also offers some full-length TV shows (mostly news and public affairs). Shown here is the full-length CBS Evening News program, available on-demand. (CNET Reviews is published by CBS Interactive, a unit of CBS.)
Amazon's Video on Demand service is also available on the Roku Player. It's a nice alternative to Netflix: TV episodes and movies are available for rental (pay-per-view) or sale (always accessible, once you buy). Much of the content is available in HD. ("Dexter," shown, is from Showtime which, like CNET, is a unit of CBS.)
Many of the Roku's channels let you search for shows via an onscreen keyboard. (To date, you can't yet search and access new Netflix content; you need to modify your queue from a separate device, such as your PC.)
This scene from an HD episode of ABC's "Lost" shows how good the high-definition image can look. While not all content is in HD, the ones that are--particularly on Amazon and Netflix--can go toe-to-toe with many cable and satellite systems in terms of image quality.
This scene from "Barton Fink" on Netflix shows a common problem. Not only are many movies and TV shows not available in HD, but also some of them aren't even available in their native wide-screen aspect ratios.
Another annoyance with Netflix: some of the TV shows (such as "Miami Vice") are missing specific episodes, likely because of legal issues over the music used. On the bright side, Netflix subscribers can just have the discs mailed the old-fashioned way.
While Netflix offers thousands of movies, most of them are older titles from decades past. Exceptions tend to be movies from the Starz/Disney catalog, which are accessible soon after the DVD becomes available.
Netflix's library of TV shows is pretty strong. Many current shows are available, and a handful--such as "Legend of the Seeker"--let you watch episodes from the current season, within days of the original broadcast.