Ergonomics are important. (It's the main reason I try to avoid mass markets. All the ones I want to read are massive and painful to hold for long.)

I'm just hesitant to spend $70 on a fancy cover until I know I'll use the ereader a lot.

Definitely! Same here. I didn't buy mine until I had my reader for quite some time and was sure I'd be happy with the added expense.

(I'm actually curious now how new generation ereaders handle nonfiction...)