Brian,
There are some reasons why an octo line is better than overlaying dual line ephone-dn's:
1) First, the 8 channels of an octo line can be shared between different phones, whereas with dual lines the phone owns both channels (forcing the call to hunt to the next dn, effectively cutting the real call capacity in half).
2) When you do a shared line with octo line, you also get "Line in Use" indication. This doesn't happen with overlays.
3) You can assign the octo dn to as many phones as you want, even though you will have only 8 simultaneous calls (this should be more than enough for most SMB deployments).
4) If you need more simultenous call capacity in a "ring all" fashion, you can use call blast hunt groups.
5) Ephone dn's come at a premium (they are not infinite and limited by license capability). This means that if you start overlaying left and right, you might run ou of ephone dn slots.
6) Octo lines can be use for other things such as conferencing.
This doesn't mean that we should completely eliminate overlay dn's. For example, you still need them if you want to add a SPA525 to shared line, as this phone doesn't support octals yet. But in general, I think the need for overlays will decline given the amount of options in our toolkit.
Thanks,
Marcos
