It could be due to the retina display. iPhone4 has double the resolution of 3GS. Drawing 960x640 pixels vs 480x320 in canvas is going to have some noticeable impact.
While it's probably not exactly what you're looking for, Safari's Snippet Editor is great for whipping up some quick HTML with auto preview. Accessible via the menu, Develop > Show Snippet Editor.
Why? He's clearly so happy with TextMate that he's willing to fork over more money for version 2 voluntarily. That doesn't sound like someone who's in need of a new editor.
You're assuming that your static assets (js, css, images) aren't served from a CDN (pretty much the standard at companies like Yahoo!). When your main server is serving just the HTML it's much more likely that your requests could double.
Welcome improvements, for sure. I've been using WebKit (Safari, specifically) as my main development browser after abandoning FF some weeks ago and these additions address many of my migration annoyances. RGB colors and easily added CSS selectors are huge.
If we could get default rendering of XML and JSON documents (like the JSONView add-on provides for FF) I would be a very happy camper.
