It will have a killer feature and at a guess the killer feature will be software.
Th killer feature will be mobile me, eventually.
This is an interessting point, if you know that apple built a new server farm in North Carolina. I think the killer feature is the content (complete MobileMe and Software)!
I got my first Apple product in the beginnig of this year, it was the iPhone, i have wait so long for a device like this and i´m very very happy about it, so i´m an apple rookie. If you see the gap between the MacBookPro´s an the iPhone it makes sense to put a product there. And you will see it will be a sort of iPhone/MacBook device. I think i would buy it, and my next computer will defintly a iMac (i wait for quad processors

, and i´m hoping it will have this slot for the tablet

) I see this for the tablet:
1. 10" Multitouch device
2. Long lasting battery (like the Macbooks)
3. Mac OS X Leopard (faster, slim, MS Exchange...)
4. 64gb 128gb SSD Drive (short accesstime, low energy consumption)
5. 4g LTE, WiFi, Bluetooth (connectivity)
6. Possibly: iChat Cam, 2x USB, Monitor Out...
7. iPhone App support, some sort of a bigger Store to buy Programs, don´t know
8. The price (700$-900$) possibly less
Why more? Why a awesome feature? It makes totally no sense! The old white MacBook will be killed and the gap will be filled by the tablet. A smarter Mac but an better iPhone with a full OS X. Think about it they have rebuild the OS X completly.And if you want something better get a MacBookPro! If you have it fine, but you are not the target group i be the target group!