Cade Metz:

Apple’s iOS mobile operating system runs web applications at significantly slower speeds when they’re launched from the iPhone or iPad home screen in “full-screen mode” as opposed to in the Apple Safari browser, and at the same time, the operating system hampers the performance of these apps in other ways, according to tests from multiple developers and The Register.

I haven’t noticed any speed difference when using Fever on my iPhone, but I rarely open Fever from within Safari. I expect to see a 4.3.1 update soon that will fix this bug.