I know a lot of guys who use the GT7, and I have three of them myself. I don't know anyone who goes outside of the various factory presets.
To switch between presets is a breeze. Hold down the setup button until all the lights flash. The number of flashes tells you the current preset.
Then press the button however many times you want to "advance" to the next preset. When you release the button a moment later the lights will flash however many times indicating what preset you are now on.
Best to use something non metallic to press the button (I use a wooden skewer).
Also the ESC is usually supplied with a nifty little decal which goes on your toolbox which summarises the programming options.
Obviously everyone is different, but I nearly always stick to 7 (slick tracks) for off road both mod and stock, and I vary between 7 and 1 (Smooth Mod) for on road, currently using "1" for my on road 19T.
I like the GT7, and for the silly prices they go for now the GTX is out, they are a great option.