Making a beautifully lush stereo phase/delay patch with two counter-complimenting amp tones, strike up a fat one and lose yourself in the sonic soundscape.
Using two amps with tone biased settings such as one high gain treble dominant tone, the other with a lower gain, bass dominant tone and mix up a thick, clear wall of sound. This can be switched up in so many ways to get a huge variation of sounds.
As others have said, lube-smooth transition from gain to clean.
Lastly, any less restriction or more enhancement on my creativity and playing enjoyment is a win in my book.