Well, Safari5 Reader's approach may make that feel less necessary - since one can easily click in and out of Reader-view.

And an advantage (as I test-drive it) is that turning the Reader-view on/off for a given article is almost instantaneous: whereas with Readability to move _out_ of Readability-View involves _reloading_ the entire page (which I find annoyingly slow on pages like TechCrunch, RWW, etc where there are tons of ads to be (re)loaded.

I think the Safari-Reader approach may increase time I spend with a full, ad-laden page open.