The two park ticket isn't much more expensive than the 1 park anyway (from memory) - I can't see it making much difference anyway, I don't actually know anyone who has gone to one and not the other... At least Universal can justifiably call themselves a RESORT and many people stay for weeks on resort without venturing anywhere else.
Universal have really outdone Disney with this I think... I understand that Disney is aimed at the younger audience, but HP is (not exclusively) for the younger audience too. Universal have a much more diverse offering as a theme park, more-so now than ever.
US & IOA have always been more highly regarded than Disney to me, (even at a young age, pre-potter) and as much as I can take or leave HP, I REALLY want to see this. Congratulations Universal, you really have pushed the bar even higher.
Why, oh why, could there not be this kind of competition in the UK? Or even this kind of EFFORT would nice! Just look at Phannyland, you could argue that they do not need to theme to such a high standard (compared to their competition) but what they produce is outstanding, albeit on a smaller scale than Universal.