What's new is the blue bar on top instead of the softer gray shade, right?

I've been seeing this for almost a week.

Philipp, correct.

Ionut, it only just appeared for me out of the blue this afternoon. I figured they might be going for this design because it doesn't use any background images.

BTW, while testing this, I also realised that setting the PREF ID cookie value to nothing reverts back to the old Google UI from before they introduced the context links.

Just for reference, here's some text from my cookie:
PREF=ID=5f635d2e39de9f14:FF=4:TB=2:LD=en:NR=10:CR=2:
TM=1179674501:LM=1180895440:FV=2:DV=AA:GM=1:
IG=3:S=PExldwPXLPOy4old;

<< BTW, while testing this, I also realised that setting the PREF ID cookie value to nothing reverts back to the old Google UI from before they introduced the context links. >>

Yeah, if you delete your Google cookie, you'll see the old bar.

> I've been seeing this for almost a week.
me too. but not for a week, already since the new layout is public.

Since now I'm getting this blue-only bar too (seems more in-tune with the other Google services, and a little bit more simplistic, which is also Google-style).

And another subtle change. They've now added a blue line to this bar:
http://blogoscoped.com/files/more/google-ui-test-blue-bar-line.png

This makes it more like their previous design:
http://blogoscoped.com/files/more/google-ui-original.png

I've just got it too. Now that I've got used to the gradient one (which I liked), this one is a bit too bold: it's distracting and I can't take my eyes off it. Very confusing. Will they stop playing around?

I hate the messing around. You should be able to choose if you want an "Experimental Cookie" and then they send you the changes.