You mean the new iMac that comes with Thunderbolt? I realize this causes problems if the internal drive dies, but for most people, the primary concern with the hard drive is expandability. It seems Thunderbolt would offer expandability at speeds that would more or less nullify this whole issue.
This is exactly what I was going to say. The fact that it has two Thunderbolt ports would make this a non-issue for me. If I needed more space in the future, I'd simply attach a Thunderbolt drive (they'll be out this summer).
I'm sure the number of people who immediately need to upgrade the internal drive on their new iMac (before the Thunderbolt drives come out) is tiny.