asterisk users - Dec 2004 - E1 and analog cards FXS in one box.

Hi all !
I want use 8 FXS ports maybe more with E1 card
from Digium or Sangoma. All together in one
Asterisk box. 

I heard that are some problems with mix analog and digital
card in this same machine.

Is that true ?? 
Does someone has this instalation ??

Thanks 
Andrzej