Hello
@mace¬
In response to your question, yes the SCUF buttons are the buttons on the back of the controller. 'Pro' players find that these buttons allow you to react faster in games. For casual gaming though, they're not really needed. Another benefit of the new 'Elite Controller' though is that the bumpers are now a lot better (easier to press), the thumbsticks are changeable, as is the d-pad - all to suit you and your gaming style. The buttons can be remapped as well. I am also pretty sure that improvements have been made to the triggers and the general accuracy all round. I hope this helps.
Moving on, regarding Backwards Compatibility.
This launched yesterday for Preview Program members (I am a member). Right now there is a limited selection of 360 games you can play on the Xbox One. The way it works is quite special. You pop your 360 game in to your Xbox One, and if that game is supported to be played on the Xbox One, your console then downloads a digital copy of the game. The game is then added to your games library, together with any 'Cloud' saves you have from your 360. The game has its own box art etc and looks 'nice' in your Xbox One games library. Now, when you wish to play the game, the Xbox 360 game disc must be in your Xbox One. You launch the game, this in turn launches a virtual Xbox 360 on your Xbox One. The virtual console then runs the 360 game (remember, its not running from the disc, the disc is only there to prove you own the game).
Now, when playing a 360 game on your Xbox One, pressing the 'guide' button will bring up the familiar Xbox 360 menu. You can chat to and message Xbox 360 players as if you were playing on a 360! Any achievements you earn will go towards your gamerscore but will count as Xbox 360 achievements. Saying that, you can still Snap TV, multitask and even stream to twitch! You can also take screenshots and record gameplay! So its an Xbox 360 running a 360 game on your Xbox One with all the features of a 360 WITH all the features of the Xbox One combined! See what I mean when I said special?
So now you may ask: "what about all my DIGITAL download games on my 360? are they now stuck in limbo?"
The answer is No. Lets say for example you have Tomb Raider downloaded on your 360 as a digital download. Once Tomb Raider becomes available as a 'backwards compatible' game, it will automatically appear on your Xbox One as a download. You can then launch it as a 360 game and play as normal.
This costs the developers of the game nothing at all, all they have to do is say yes to Microsoft making the game available on Xbox One and MS does all the work. As long as you own the game disc or have the game downloaded digitally, it costs you Nothing! Pretty damn cool!