I just bought one of your Hifiberry Digi. It works really fine now, but it took me some time to get it working. This was mainly because there is much information how to get the Digi working with openelec and an experimental built. This was correct in may I think, but since there is a new version of Openelec it's much easier to get it running.
If you are using openelec 4.0.7 stable you can follow this guide to get hifiberry running:
Install the hifiberry and start your raspberry.
The green light should turn on (if not there's something wrong).
SSH into your Raspberry.
Use the command
cd .config/modules-load.dto jump into the right directory.
There you should build a new .conf with
nano hifiberry.conf(it opens the editor).
Now you have to activate some modules. In short just add the Code below:
Close the Editor and save the hifiberry.conf.
The problem now is, that you can't use the omxplayer any more (it doesn't support ALSA driver as far as I know) so you have to use the built in dvdPlayer. You can make it your standard player with a little more code in your advancedsettings.xml.
If you already have an advancedsettings.xml, just open it and add the code below. If you don't have it, you should consider .
So now make the dvdplayer your standard player:
After a reboot (if you're still in SSH just type "reboot") the hifiberry is available in your xbmc-settings and everything should be fine.
If you have a dts or dolby-digital (AC3) capable device plugged to the hifiberrys spdif, you can use passthrough to have surround sound.
I hope it helps to get your hifiberry up and running with openelec.