Actually, those list apps don't need the pen to cross them out. Usually a single touch marks them done (in the cart etc.) in some visual way. The best features of the list apps IMO are:
multiple lists: I can have a list per store, or even inrelated lists (ie. vaction packing lists), all in the same app so
I know where they are. (I lose paper lists, memos, reminders, sticky notes etc. They fall behind me like snowflakes
)
Recurring list items: the list apps keep a database of what's been entered before. I can pick items off a list, rather than re-entering.
Notes can be attached to items: Very important when picking up items for some-one else. Makes the description in the list much smaller, but can be called up when you are at the store and presented with a huge display of similar products with different names, sizes, colours, scents etc.