The source data is stored on the disc (HD-DVD or Blu-ray) at 1080p/24 and is interlaced to 1080i/60. Your television should be able to properly deinterlace the signal to 1080p, and you will see the exact same picture. This 1080i/p thing is worthless marketing talk.
If you have a 1080 set that can play in 24Hz multiples, then you probably have the money to buy a better player that can output the native 1080p/24 signal to the set.
For the rest of us with 60Hz televisions, this 1080i issue is moot.
What about the new 120hz and 150hz sets?
All blu-ray players can output directly in 1080p/24, 1080p/30i, and 1080p/30p.
Only the XA2 and the 3rd gen players have that native ability.