Here we go:
Renault - The blue and yellow combination is rather lovely, but, as Dave mentiond, the dark blue spoils it, it was much nicer in 02/03. Also, looks rather cluttered in places.
McLaren - Great idea with the chrome car, in the right light it looks fantastic, red needs to be darker.
Ferrari - Nice livery but I do wish they would go back to the scarlet red of old.
Toyota - Still pretty much the same livery as forever but it's clean and works.
Williams - Nice livery, looks gorgeous on this car but the pre-season livery was better even on the FW27, can only imagine how good it would look on the FW28.
Honda - The biggest dissapointment for me this year. I was hoping for something along the lines of the '60s GP cars or the Accord/Civic touring cars of recent years, but no, it's last year's BAR (the worst of the BAR liveries) with the Honda shade of off-white. What would be better would be either the Lucky Strike livery of the '99 car or a 555 car instead.
Red Bull - I've always liked the Red Bull livery, clean, simple and not cluttered at all.
BMW Sauber - I was expecting more (and a tad of Petronas green) but it's another clean and simple design that works.
Midland - When I first saw that top down artist's impression I thought it was a cool blend of colours and simplicity. Unfortunately, the shade of 'red' is nowhere near what they originally posted and the mass of sponsors really spoils this car.
Scuderia Toro Rosso - Great idea that doesn't work quite as well in practice. Thumbs up for trying something new though.
Super Aguri - Quite a nice little livery I think, might look better on their own chassis, though. Looks more like a Honda than the Honda does!