Just thought I'd weigh in since I'm the author of the app. I was pleasantly surprised to see my little pet project from a couple years ago make it onto hacker news, since this is the first site I go to to read my daily news.

Anyway, the intended purpose for spreeder is not to supplement your reading (I personally don't use it for that purpose), but rather as a training tool. The one (and probably only) thing I got out of any speed reading training course was that there's a lot of redundancy when reading texts.

People "read" text in their head (subvocalize), which slows down reading (vs just seeing + understanding it). Also, most people tend to reread a lot as well since they're not focusing.

Spreeder is meant to be a trainer of sorts. When words are flashing at a high speed in front of you, you're forced to focus more on what's going on, and you don't get a chance to reread things you missed. So you're naturally inclined to pay more attention. When I want to train, I read at a speed where I can barely keep up - it helps eliminate me naturally trying to subvocalize the words in my mind.

In the end state, I've found it's helped me in my normal reading. I don't actually use spreeder to read my daily dose of internet stuff, but I spend less time in the unfocused state so I get more out of it.

Just my two cents.