I guess you don't know what you are missing until it's gone. But looking at the screenshots from WP8, it just looks so much like a cluttered mess. In comparison, on WP7.5 it's almost like the tiles have "room to breathe", all thanks to the blank space on the right while with WP8 it looks like the phone is about to explode with live tiles. I don't want a ticking live tile bomb! So I sincerely hope that Microsoft is either going to make it possible to arrange tiles in such a way to leave a comparable amount of space blank on the right side or simply make the gutter a show/don't show option somewhere in the settings.
I absolutely love what they are doing with the start screen. In my opinion the resizeable tiles beat folders hands down. But especially with a OS so focussed on having a clean and nice to look at UI, getting the negative space back is important.
Are you disturbed at the "cluttered mess" or that they eliminated your "breathing room"?
In my opinion, Microsoft erred in revealing the new Start screen the way they did. The truth is that, even though tiles can now be resized to one's liking, it can still be made to look exactly like Windows Phone 7's Start screen (sans the "gutter"). I believe they would have spared themselves a lot of negative commentary had they simply introduced a new, "guttlerless" Start screen and simply demonstrated WP8's new ability to resize tiles.
Personally, I really, really like the new Start screen and look forward to picking up a 4.3" 720p Windows Phone 8, but I do believe the way in which they introduced the new Start screen was pretty jarring.