This is an answer to Question #2 posted during the Webinar on 11/14/07 on Core Networking 6.4:

Q: What is the biggest difference between io-net and io-pkt drivers? (Hint: it has to do with the way the initialization
 routine is used).

A: the stack uses a ‘shim’ layer (dev*-shim.so) to translate from io-net to the networking layer (Core Networking 6.4)

(I think that was mentioned during the presentation.)

Besides, 
•io-net drivers export /dev/en<N>
•io-net driver can be unmounted (by using umount /dev/en<N>), while io-pkt can be destroyed (e.g. ifconfig eth<N> 
destroy)
•io-net drivers use dedicated commands (e.g. speed, duplex) to set different modes, while native drivers uses ioct 
calls.
(these can be found at the Networking Wiki) 

Regards, 
Vlad