Sorry I'm late. Here are all the answers to all of your questions...
This is a Roku 3. It is the best supported and most powerful Roku. It's not the most recent model, and, in my opinion, it's not the best.
The Good: It's 5x faster processor than the others. It is the best supported model -- the YouTube and Netflix updates hit this model first.
The Bad: No composite out. Even if you do not have an older TV with no HDMI, composite audio is a very cool feature. You can route this audio out to a soundbar, a receiver's aux audio, or even amplified speakers so you can listen to Pandora or Spotify without running your TV.
The Ugly: WiFi remote! To allow you to listen to audio via an earbud jack on the R3 remote, they stream remote commands and audio via WiFi. This causes interference issues including choppy sound and an unresponsive remote. Worse, when your WiFi router is interfered with, it throttle speed to improve connection quality. Of course, if you do plug earbuds into that jack, keep a box of batteries nearby.
Here is a chart comparing the features of all the currently available Rokus including the veneralbe Roku 2 XS which is my favorite...
Here is another chart comparing the processing power of the various models...
It's easy to see that this Roku is much faster than the others, but, since the Roku has been streaming HD for years and the Rokus released after this one reverted to a slower processor, you might wonder what all those extra bogoloops are doing for you.
Back to the questions...
Q. Can this play files from an NFS mount.
A. Maybe. They have to be in the right format and there has to be some kind of server software in the mix.
Q. Is the new stick a Chromecast killer.
A. No it is a really inexpensive variant of the Roku 2 family.
Q. What does this offer that my other streamer doesn't?
A. Whether you have an Xbox, a SMP, or a BD player, it's all about the channels. Compare the content your current streamer can play to what you see at http://www.roku.com/channels. Read the descriptions carefully because the Roku Fox News Channel IS NOT what you get on Comcast.
Q. What do channels and content cost?
A. Some apps (channels) cost money, some apps (Netflix, Hulu, Amazon, MLB.com, etc.) require you to pay a monthly or annual fee for content. Some charge for the app and again for the content. Some require you authenticate with a cable provider. There are some very good, free apps...
Out of the box, your Roku will have THOUSANDS of channels (apps) of programming. These channels may free or you may have to buy them. You may also have to pay a monthly or annual fee for content. Netflix, MLB.com, and Hulu are free apps, but you have to pay for their content. Here are some free apps with free content...
ADC: Free movie channel
Amazon Cloud Player: Play all the free music Amazon sends my way
CNN: Includes CNN International Live for background news and information
Crackle: Sony’s FREE version of Netflix
CS50: Harvard Intro to Computer Science course
Comedy Time: ‘Play All’ makes for good background noise
CBSSports.com: ‘Play All’ feature makes for a nice sports news channel
CNBC: Streaming business news for news and information
FoxNews: Stream from web site plus clips of popular shows with ‘Play All’
Kaplan College Prep: Help your kid with his SATs
Lecture Kings: Librivox audio box is hidden in a channel of university lectures
OVGuide: Free movie channel
Popflix Classic TV: 26 Men, Adventures of Robin Hood, The Beverly Hillbillies, Bonanza, Burns and Allen, Date with the Angels, Dragnet, Life with Elizabeth, The Lone Ranger, The Lucy Show, Man with a Camera, Petticoat Junction, Sherlock Holmes, Westerns, You Bet Your Life
PubDHub: The stuff your dad used to reminisce about — ancient cartoons, PSAs, commercials, and movies
Smithsonian: Better than the Discovery channel
TWiT: Steve Gibson, Leo Laporte, and others talk tech
WSJ Live: WSJ had good election coverage
Q. Can I watch live/local television on my Roku?
A. If you like local programming/broadcast television, Aereo [aereo.com] streams these for $8 (one set) to $12 (two sets) per month. Aereo includes a 'cloud DVR' as well. Aereo works well, but many complained about buffering during the Superbowl and it is on-demand, so after watching the Big Bang Theory, you bounce out to their menu and select Two and a Half Men, etc. (In April the Supreme Court will hear a case that may determine that Aereo is not legal; google is your friend)
Q. Why are there so many refurbs?
A. Because Roku is not the same as cable, networking is hard, the internet is getting congested, and the cable guy won't come to your house and make it work. This is not a toaster. A lot of people find making things work a lot harder than expected and the results a lot less than promised. Good for the rest of us, right?
Q. Why don't these have a slot for a cable card?
A. Because they don't.
Q. Is the Plex channel free?
A. No it is not. It's been $4.99 since December.
Q. Should I get a refurb?
A. (Sorry Woot) Some have complained that Woot and Newegg have been really bad with refurbs -- shipping junk and not supporting their customers. I've only ever had one problem with a refurb (R2XS remote) and Roku shipped me a new one right away. Call Roku if you have problems. DO NOT USE their forums unless you need exercise. RokuShawnS et all will have you running around in circles and jumping through hoops.
Q. Can I watch YouTube on my Roku?
A. YES. The Roku 3 (this one) has an official YouTube app. For other models, check out VideoBuzz.
Thanks for the plug inirons and happy streaming to the rest of you!
PS, I think the Mohu Channels is going to be a lot of fun. Be sure to check out their Kickstarter project before it closes!