They all look pretty spot-on to me.

Arabella portrayed Matilda in the West End production of the musical, and seems very Hermione-esque in this image:

It's also great to see that she can pull off a bushy hairstyle. No offense to Emma Watson, but that's one aspect of Hermione she couldn't really do properly:

Dominic's eyes aren't green, but they're pretty close:

And his absolute eye colour doesn't really matter, just as long as whoever they cast as Lily matches his.

Alastair's eyes aren't blue, but I believe Ron's eye colour is only mentioned once in the books and plays no role in the plot.

Now we just need to see how good their acting chops are...