Here's a macworld article about Apple TV vs. Roku:
http://www.macworld.com/article/163...roku_set_top_box_which_is_right_for_you_.html
Summary quote at the end:
"Broadly speaking, which path you take will be determined by your desire for local or Internet media. If you have nearly all the media you want in your iTunes library or on an iOS deviceand can make up for the media you dont have with Netflix streaming videothen the Apple TV is a good fit. If, however, you seek nearly everything the Internet offers in regard to streaming media, the Roku devices deliver exactly that."
Disclaimer: I have not used Roku or the Revue, only the ATV, so I am probably biased.
My main interest in the Apple TV when I purchased it was the ability to easily view photos and home videos on the TV without having to hook up my computer to the TV every time. Since I use iTunes and iPhoto anyway, the ATV worked perfectly for this, as I don't have to take ANY additional action after importing my photos to iPhoto. They just are available to show to family and friends on the TV. The Roku can't do this. So if viewing home media on your TV easily is important to you, then ATV is your only choice, especially if you have a mac. (If you are using a windows pc or some other photo software, you can still have ATV just watch a folder containing photos.) This was important to me because we have young children and take a lot of pictures of them. So I could imagine not everyone would find streaming of home media as important.
As for media streaming options, Roku may seem to have more, since it has many "channels".
http://www.roku.com/roku-channel-store
However, a lot of these channels probably just present you with a choice of pre-selected short videos to choose from. This is essentially the same as the video podcasts available on the Apple TV for free.
http://gigaom.com/apple/watching-video-podcasts-on-your-apple-tv/ There are literally thousands of different sources for video podcast content on ATV. So I'm not convinced that the Roku actually offers more real content than the ATV.
People have mentioned Hulu. Yes Roku offers a Hulu Plus channel out of the box, while the ATV does not. But in my view, Roku actually is more limited than the ATV in this regard. On the Roku, you only have access to Hulu Plus, meaning that if you don't pay the Hulu Plus subscription, you get nothing from Hulu. In contrast, you can simply jailbreak your Apple TV, install a Hulu plugin, and have access to both the free version of Hulu (if you don't want a subscription) OR Hulu Plus (if you do). Instructions on how to do that are here:
https://forums.macrumors.com/threads/1305573/
(You can also install an Amazon Instant Video plugin using the same method, if you are an Amazon Prime member.)
Finally, if you have an iphone, ipod touch, or ipad with Airplay capabilities, the ATV is a no-brainer. The ability to wirelessly mirror your iDevice screen (for the iPad 2 or iPhone 4S), or send video or photos or audio straight to your TV screen/speakers without having to plug anything in is really quite useful. Roku doesn't offer that.