Definitely going to be pre-ordering this whenever Nintendo announce a price. I think the price of this system will be paramount to it's success. If Nintendo want to compete with the 360 and PS3 (which they'll have to do) then I really think around the £250 would be about right. Amazon.co.uk listed the console for £199.99 but withdrew the listing hours afterwards, but they did say the price came from their suppliers.
Regardless, I'll be getting one. Mario and (hopefully) a proper 3D Pokémon game would be huge selling points in my opinion, and I'd rather get AC3 on this than on my 360, just to see what this thing is capable of!