I was at the fest today and used the paints quite extensively, my thoughts are as follows...
In general I think it's a fantastic product. I work in a technical role for an ink manufacturer so the marketing stuff won't really wash (🙄 with me. Make no mistake, what these paints basically are are washes with more pigment, so when you put a red contrast paint over a white undercoat it won't just tint the white to a pink, it will make the whole thing red. One of the guys on the stand was trying to tell me certain things like don't use a palette, don't water it down, just throw down as much as you can in one go. If you do that you will get poor results, just like you would if you used washes like that.
Interestingly, I also watched a demo with an 'Eavy Metal painter, where he demonstrated using the contrast paints over the current range as glazes and washes essentially.
When it came to using the paints themselves, the range they had for use was somewhat limited and didn't necessarily fit the models provided, so I just tried to use the more interesting colours to get a feel for what they looked like. All colours are just one coat over the base primer, which is indeed one of the new contrast ones. Here are some pictures of the results I got...
The flesh looks really great in my opinion. The blue is a really nice colour but looks a little sloppy in places. Probably my own fault.
The black gives a pretty good grey to be honest, and I was really interested in these 3 brown colours for options of painting things like leather. I think they look good but maybe not much better than simply painting mournfang brown + agrax earthshade or similar. My favourite here was the glove colour which is called Gore Grunta Fur.
This I thought was a pretty cool cloth colour.
Example of a red and yellow.
It's pretty obvious from the pictures above that they're not going to make your models look professional with a single coat, but I do think it'll be a fantastic tool to paint some things very quickly. Already I'm thinking about things I'd like to use them on like painting large numbers of grots, orcs, free people soldiers, sylvaneth etc.
There were also some examples of finished models that had been supposedly painted exclusively with the contrast paint.
All in all I think it's going to be a very useful product to add to the painters' arsenal and it'll help me paint quicker, particularly with units. I'm a little nervous on what the price is going to be but I guess time will tell...