Been using various iOS 5 betas (and now the GM) for awhile now. One of my favorite features (besides proper notifications, of course) is Safari Reader. Basically, it strips away all the cruft from a webpage and simply displays the content you want to read. It works similar to things like Readability.
It’s especially nice, since it presents the content in an eBook like format and you can dynamically resize the text.
Something I find interesting though — I haven’t really been using the “Reading List” feature. Basically, it’s a way to temporarily bookmark articles and websites you want to read late. As far as I can tell, it doesn’t do offline access though (so, I’ll still be sticking to Instapaper for my offline needs).
More info on Apple’s website.