My regular ride 2005-2007 was a Look 251, a very similar frame. Lovely ride in many ways, very smooth but it was distinctly flexy in the front end - I had very low confidence on it going fast downhill and cornering - and I ended up selling it for that reason.
Actually, the later Looks of that design are meant to be much better in this regard (e.g. KG381/481) - they beefed up the tubing stiffness - and I'd be very tempted to pick one of those up if the right one came on the market.
Otherwise, steel... well, you wouldn't be mad, the weight penalty is not so great on newer steel frames (my Look weighed in at around 2.2kg F&F IIRC - my Concorde Columbus Genius is 2.8-ish, with a lot of that in the fork). But I guess it all depends what you want out of a bike - decent alu frames (I also have a newer alu/carbon mix) are excellent and great value, and more suitable for racing/riding up hills on. That said, I'd sell my alu bike before my steel
In other words, get the right frame and don't worry so much about the weight!