From Federico Viticci's post 11 Tips for Working on the iPad:
[Here's...] a list of my favorite long-press shortcuts in Safari.
9: Tap and Hold in Safari
Safari Reader (text icon on the left side of the address bar). Display settings to always use Safari Reader on the selected website or for all websites.
Considering how much I've missed per-site Reader activation since last I used Safari on MacOS X (where I used CustomReader to achieve precisely this effect, I have to wonder Why Was I Not Told About This?
The thing is, I have no doubt that that feature got the odd mention in any number of reviews that appeared when it first appeared. If Apple are going to hide it away behind a long-press shortcut, I have to assume that Apple are OK with users not being aware of all the features they roll out in iOS once a year or so. This is where an operating system with a menu bar wins every time...