Indeed, the Mobileread.mobi site is quiet usable on the iphone, and I usually spend about 30 to 45 minutes using it everyday.
Yes while some links can be a bit hard to hit in Portrait mode (Last read, next, etc) especially if you have fat fingers like me, a quick pinch in solves that and just using Landscape mode would sole a lot of the ergonomic issues.
While a iPhone specific page format would be nice, it would probably not help with the main problem I run into, typing long reply's using the iPhone virtual keyboard

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