Fast (concave) fades work better for ends of songs; slow (convex) fades are good for truncating sound bites. Option-clicking on Peak''s fade-out button brings up the curve-adjustment window instantly. (The blending button is circled.)
One of the secrets to making smooth audio edits is to cut on a zero-crossing, the point where the waveform crosses the centerline. Like many editors, BIAS Peak can snap to zero-crossings automatically, and that works well when you're snipping percussive sounds. With flowing sounds or ambience, though, you'll usually get better results by enabling Peak's blending mode, which crossfades the audio on each side of the edit points. You can switch between modes instantly by pressing the Caps Lock key. When I'm having trouble making a smooth edit, I'll toggle the blending mode each time I adjust the edit points. That makes finding a seamless transition faster.
Another frequent editing task is applying fades, and Peak seemingly requires an annoying five clicks to change fade curves. Fortunately, Option-clicking on the fade-in or fade-out button brings up the curve window instantly. (For more about David Battino's work, visit www.batmosphere.com.)