Hey, I got a E53 X5 this year and love the space. I drove an X3 as well and compared to the X5 it is a little cramped.
If they say that the X1 is marginally smaller than the X3, then my verdict is that I like the look of the X1, and I will live with the space it provides, eventhough its should be small, but then they have to make it worth while with the pricing.
They are probably going to price it equal to what an E53 cost in 2004, which makes this "small more entry-level" a little out of reach for the lower end of its target market.
We will just have to wait and see...