As much as I usually dislike change, I do think this could be good for the site. At the moment this is very new and obviously will need a few tweaks such as in the layout where things don't line up completely, but two features that this update will NEED to work for me is:
1. Option to disable resize when submitting content - obviously some flash doesn't look good when resized, and some just completely lags itself into oblivion. And resize isn't always necessary anyway.
2. Option to disable auto-play on user accounts - some people use newgrounds differently to others and so this auto-play feature wont be helpful for everyone. As said by others it can really lag and I really don't mind clicking play myself.
I find it must be so annoying whenever websites have an update after months of working on it and the users turn round and say NO TAKE IT BACK YOU HAVE WASTED YOUR TIME TRYING TO MAKE THINGS NICE FOR ME.