Nothing fancy. Soft buttons are software / programmable buttons... Certain areas of your tablet can be programmed to do specific commands. You tap the region and initiate commands like cut copy paste etc... I use it for clone, feather, select dodge, burn etc... It is much faster than using menu's.
For example, the dark spots in the picture can be programmed (shortcut key mapped) to perform different functions...
I don't know if you have set up such programs in windows that allows you to move your mouse to the Top left corner and you can start some application!
This is similar but specific to the tablet. you can program many many (sometimes 40+) functions on designated tablet areas. May be you can label them and save time while editing.
I typically find this easier than going the menu route so that I can concentrate on the picture. You can literally hide the stupid toolbars and work on your PS full screen.
Intuos is targeted at the Pro market and Graphire at the consumer market (at least that's my opinion). I think they are very similar except that Intuos may have certain nicer features (pen comes with a reaser function if I am right). Intuos is compatible with a number of accessories that wacom makes. Graphire on the other hand gets little support. I guess Intuos comes with an optional mouse too (not sure about graphire). Honestly, the mice is nice to have.
The differences matter if you spend more than 4+ hours per day (day after day) on the tablet. If you spend 1-2 hours per week, you might have more reason to look at cheaper alternatives.
Anyway, for the money, Wacom tablets are really ergonomically designed (both the pen and the tablet) and comes (I believe) with a licensed version of Photoshop elements.