Well, after leaving my PC on all night, the Beta had finished downloading this morning.
I have to say, it's bloody impressive for a Beta. Far more polished than Project Cars, I think it lacks the 'scariness' of it though. I use both the throttle and brake far less carefully in Forza - knowing that I can probably catch it if things start to go wrong. Forza clearly has a lot more on par with the likes of Gran Turismo than Project Cars, but that isn't necessarily a bad thing. With Project Cars, I can't play it well at all with the pad. I have to setup the Logitech wheel and be committed to playing it. With Forza, it's totally controllable with a 360 pad - and I think that's where it's 'quick 20 minutes' appeal will win over Project Cars.
As Andy says (
@SharkyUK) - it's not yet capable of supporting multiple GPUs. How the hell Turn10 have got the game I played running on my PC using effectively just one GTX680 with 2GB is an amazing feat of programming. The game barely seemed to have any slow down - even in crowded corners. Strangely, the only issue I saw was the occasionally 'jerky' rear view in the mirror - yet what was out in front through the windscreen played really well indeed.
I'll be buying it for sure.