"Well, we’re all in showbiz now, walking on eggshells, relentlessly tending our customer base. We’re all selling something today, because even if we aren’t literally selling something (though thanks to the Internet as well as the entrepreneurial ideal, more and more of us are), we’re always selling ourselves. We use social media to create a product — to create a brand — and the product is us. We treat ourselves like little businesses, something to be managed and promoted."
1. It just works - I have never encountered an issue with the bookmarklet not formatting an article correctly.
2. Day vs. night mode. You can configure it to automatically switch to white text on a black background at night.
3. Performance - even with 100+ articles the app doesn't slow down and downloads new articles in seconds. Switching between articles and scrolling long articles is liquid smooth.
Overall, you can tell just by using it that a ton of thought was put into the UI.
For books published by the Pragmatic Bookshelf, you should link directly to the publisher, in my opinion. PragProg.com sells DRM-free ebooks (in pdf, mobi, and epub) for cheaper than Amazon. They are a great value and I bet the PragProg folks keep more money this way, which is a good thing.