Well, I like the idea of this scheme, even though I love using frames...
As for the speed? It may make the initial first page come up faster, but remember, every time you load a new page now, it has to load the html for that top section now... Thus slightly decreasing the speed of all the other pages...
But I still prefer this, it is a little easier to get used to...
A suggestion: I think that all the buttons, and or links (as well as the old newgrounds logo) should be put together into one swf... that way, it would decrease the loadtime, since the flash would only have to load once, and the html would be decresed... Also, it would fit together a little more fluidly, if all the buttons where better organized, and look similar... I miss the little graphics next to the old buttons, but perhaps new ones could be put into the background of the new buttons... The quick access bar, and the search bar should also be integrated into the flash piece... Not to mention the advertizing bar (if possible, I know some companies check html, not content)
You could add flash detection java-script into the top section of the front page, and bring up (instead of the navigation flash) an explanation of why they need flash (if they don't have it), and how to get it.