The new compositor is in trunk.
What a milestone for Blender history!!! 
Can’t wait to use it.
A big thanx and a huge hug to all devs!
You’ve just made my day.
It’s soooo awesome but I get crashes on render. I put up a bug at the tracker. I really like the ability to scale the render in the properties panel, so that you can have a low quality render as you construct the nodes. Also you can change the size/quantity of the tiles.
Well, for a while I thought I was the only one excited!
It’s so fast, responsive, and smooth that it blows my mind. Oh, and it’s rock-stable on my Linux box. Never crashed and I have been playing with it non stop for a few days. It was crash-happy way back in February when I compiled it to give it a go.
I will probably be flamed for saying this, but the new compositor feels…uh…almost better than sex! 
Btw, on the top of what you mention, I’d add OpenCL support. You can imagine how much faster it would be if a GPU is also used.
Once I scale down the output and setup the preview quality I can ALMOST scrub the timeline for feedback. Very cool.
You mean like from the compositor or from the VSE?
Nah from the compositor and it depends on the number of nodes. Color correct is ok but keying is less quick. You still can’t have the output from a node scene appear in the VSE. At least proxy render goes quickly.