I mostly get anthologies when I'm interested in the majority of it. I won't buy one simply because "it's got a piece by Wally Writer. I love him!" I mostly read from beginning to end.
Landscape reading depends on the device. On the Kindle Keyboard I usually won't. I have to manually change to landscape mode and the controls are harder to use. Touchscreen device with automatic rotation? Landscape mode is fine.
Lines vs. stanzas? I'd be more inclined to protect the lines.
Persnickety writers? Tell them to ship a large-screen reader to every customer or learn to accept limitations.