I stumbled upon a great explanation of UX (user experience) vs UI (user interface)
It was Tweeted by Jennifer Aldrich of userexperiencerocks.com. I retweeted, she thanked me, and I responded by saying:
@jma245 You’re welcome. Great explanation that UX != NULL && UI != UX && UX > UI.
For those not fluent in geek, I’ll translate.
People tend to understand the notion of UI (user interface), probably more specifically GUI (graphical user interface). They understand that buttons and menus and things you can click on and tap on, all that pretty stuff on screen — that’s GUI. Or well, that’s UI. But you see, there are more user interfaces than just a graphical one. For instance, some apps have a scripting user interface, that allows a user to interface (!) with the app and drive it with scripts to help make the app do custom things unique to your personal needed workflow. Not to get too geeky, but the point is the user interface are the parts that the user interfaces/interacts with. So, the bike handlebars, the seat, the pedals.
Yes, user interface is important.
But what most people aren’t aware of is that there’s a greater concept: user experience (UX). The UI (or UIs) are part of the user experience, but what’s more important is the experience the user has when using the product. Ever use something that was so awesome you thought it was magical? You kept playing with it merely because there was a sense of awe, of “wow”, of “cool”, of whimsy or whatever. It was just so damn awesome you fell in love and had to show it off to all your friends. Or ever have something that as you used it you found yourself getting slowly frustrated, and next thing you know you’re bashing the thing, screaming, and wanting to throw it across the room?
This is user experience.
Many people do not consider user experience, but the user experience really is the key. It doesn’t matter if your UI is pretty if it sucks to use. Conversely, the UI may be nothing special, but if the experience is awesome, people go forward with it. While we love promoting reason and rationality, in the end we’re human — we are creatures of emotion. Our emotions will drive us, and it is the experience that plays to emotion.
We must acknowledge that UX exists (UX != NULL).
We must be aware that UI and UX are two different things. (UI != UX).
We must strive to make the experience better than the interface, for the interface is merely part of the experience (UX > UI).
Strive to make the UX awesome.
Stuff From Hsoi 
UX matters on even the simplest devices. For example I have a very inexpensive coffee maker. It’s the most cumbersome POS I’ve ever used. You’d think a simple device like this would be a no-brainer.
And of course, like many others I absolutely adore the UI of my iPhone. Such a complex device. So easy to use. Amazing on both ends of the spectrum.
UX is involved in everything — not just software. You’re right, even things like a coffee maker.
In a lot of ways, good UX means that the thing is unremarkable. That it just works, and you never notice. Granted, that kinda sucks for our ego gratification, but really, it’s good because it means things are well-designed and just worked as people expected. Because believe me… if it doesn’t work, you’ll hear about it. And if you can make it something that makes people hold their breath and gasp and gaze in awe… well, that’s something special then. We all strive for that.