If you have not used an application that has "tilt scrolling"... you are missing out. Tilt scrolling enables smooth, touch free scrolling of long articles... basically tilt your iPhone to scroll up or down the article you are reading. After about 30 seconds to adjust.. you will wish every reader application had this feature.
For me tilt scrolling is now a must have, I was introduced to tilt scrolling while using Instapaper Pro, the excellent off line web reader. Instapaper will change the way you read web articles on the iPhone, any article that is more than 2 or 3 paragraphs I mark for "read later" and read it in Instapaper text only view. Instapaper gives a full screen view of the text in your font of choice with light background or dark background (your preference) and you can scroll handsfree... no more flipping each page with a finger swipe. I can not recommend Instapaper Pro enough, this is a must have application + service at 3 times the price!
I just discovered that FileMagnet ($4.99) also incorporates the tilt scrolling feature. FileMagnet is an iPhone file moving, storing & viewing application. FileMagnet is compatible with all the common file formats: PDF, DOC, iWorks 09, pics, movies, etc. Moving the files from your desktop to your iPhone is simple, just load the desktop software... no typing IP addresses. The number one reason I just switched to FileMagnet, I can now read my lengthy PDF document with tilt scrolling on the iPhone, no need to lug a laptop around!
Applications I would like to see tilt scrolling implemented in: Kindle for iPhone, Evernote, Tweetie, News apps (USA Today, NYT, AP Mobile News & WSJ), Apple's Photo albums and Safari.
... Tilt Scrolling... "Try it, you'll like it."
BONUS Tip: Give Me Something to Read