I don't know, it kinda sounds all in one (minus the angry birds maybe)
Roku 3500R Streaming Stick Product Features:
-Compact stick design. Plugs discreetly right into the HDMI port. Great for wall-mounted TVs.
-1,000+ entertainment channels and counting. By far the most movies, TV episodes, sports, news, music, kids’ shows, and free channels of any streaming player.
-Control with included remote. Comes with a simple-to-use remote that the household can share. With RF technology, you can use your remote without pointing it at the TV.
-Or control with your smartphone and tablet. Download the free Roku iOS or Android app to choose what you want to watch on your Roku player via your mobile device. It’s your choice.
-Send to TV from mobile. With apps from Netflix and YouTube, cast videos from your smartphone or tablet straight to your TV.
-Display personal media. Send your videos, photos and music stored locally on your smartphone to your TV screen with the Roku app.
-Find what you want to watch. Roku Search makes it a snap to find your favorite movies and shows from top channels like Netflix, Hulu Plus, HBO Go, Amazon Instant Video and VUDU. Even compare pricing.
-Channel shortcut buttons. Jump straight to favorite channels such as Netflix and Amazon Instant Video with the push of a button.
-Stunning HD video quality. Immerse yourself in the action with rich, vibrant video streaming in up to 1080p HD.
-Dual-band wireless. A robust extended-range wireless connection seamlessly streams video with ease and speed.
It doesn't outright say it is a mini Roku that plugs into the HDMI port, but I suspect that is what it is. and it allows streaming from your portable iOS or Android device ontop of Roku features.
Now I have to go see what the Chromecast offer out of the box to see if the Roku version would be worth an extra $15.00
edit:
-Stream online video, music to your TV using your smartphone, tablet, or laptop; Available for Windows computers running Windows 7 or higher.
-Supports Netflix, YouTube, HBO GO, Hulu Plus, Pandora, and Google Play Movies and Music mobile apps as well as select content through Chrome browser
-Works with Android, iOS, Chrome for Mac, and Chrome for Windows
-Easy setup: Plug into any HDTV and connect to your home WiFi network
-Box includes Chromecast, HDMI extender, USB power cable, and power adapter
Sounds like Chromecast will display pretty much anything from your handheld device, but you have to use your handheld device.
So the unique feature(s) look like:
Chrome:
+ putting a single tab from your Chrome Browser up on the TV.
+ Streaming of your Google Play Music & Movies to your TV/connected Stereo
+ HBOgo from your phone to your TV
Roku:
+ A Roku the size of a USB stick (all channels - TV, Movies, Netflix/Hulu/Vudu/) <no mention of games>
+ Does everything (locally stored only?) personal digital media (videos, pictures & music?) from personal handheld device to the TV like a mini Plex Server
Edit 2: The Roku Stick is basically a Roku 2 with a different remote (more buttons, but no headphone jack)
http://i61.tinypic.com/aep2qr.jpgI think I'll hold out for the reviews on the Roku stick. seems like a much better value for me personally.
$50 for an extra Roku sounds awesome if you ask me. I might buy 2 if they are any good.