Ease of Use is a major factor in Micropayment, but no one knows for sure how much of a factor it is.
My guess is that if all that stands between the user and paid-content was a hyperlink titled "Read for 25¢ IOU", most people will click through. Actually billing takes place when the amount owed to a particular site goes over certain amount ($10 sounds reasonable). At 25 cents, that's 40 articles you can read before you are asked to pay. I would guess further that most people who like to read will opt to pay the bill even if they decided to stop reading content at the site. If they refuse to pay, then service is degraded in some way for the user.
The scheme outlined above will exhibit different results depending on the type of content and target audience.