3G is nice, and I think when Apple figures out how to add it in without being a major battery drain (i.e. so the iPhone isn't like the Samsung Blackjack), it will be a nice addition.
But from my time using an iPhone so far (I haven't bought one, just tested a few out with EDGE at the Apple Store and the AT&T Store), I would gladly take the iPhone + EDGE over a Blackjack, Cingular 8525 or Treo 750w with 3G any day.
My current phone is a Treo 650 (EDGE), but I had been looking at various 3G smartphones because I liked the idea of a much faster smartphone. Browsing the web with my Treo 650 is painful; it takes forever, and once a site does load up, its terrible to navigate through. I've gotten to the point where I only load up WAP versions of sites now.
Now, you'd think that a Treo 750w or Cingular 8525 or Blackjack (all with Windows Mobile, all with the mobile version of IE) would be much better, since they have Mobile IE and 3G.
And I will admit; compared to the iPhone, an intensive site like cnn.com does load up quicker on these devices.
However, once the site loads up, navigating through a complex web site on mobile IE is a huge pain; the rendering is ugly, navigating through the site is difficult, you can't really quickly get to specific parts of a page.
So yes, the iPhone is slower with EDGE; but first, it seems like the iPhone does a great job of loading up text on a page while the rest of the page elements, etc. load up (something my Treo 650 doesn't do well), so it is possible to start reading and browsing fairly quickly while you wait for the graphics to load up, etc.
But once the site is loaded, navigating through it is a pleasure......... the time I "lost" waiting for it to load up over EDGE is easily made up over the ease of actually navigating through a site and reading it.
So yes, an iPhone with 3G would be quite good, and when it comes out it will be very nice. But as it is, right now, I would take the iPhone with EDGE over any smartphone with 3G any day of the week.
-Zadillo