Typically there are two parts to the dialer, the one you see when you dial a number, and one during a call. In all other versions of android I have run, when you leave the in call dialer to do something, then want to come back, you could click the phone button and you would return to the in call dialer.
This worked with stock, and with dialer one.
On this rom however if you make a call, try calling voicemail for example, then hit home to look at your calendar, when you hit the phone button again, you will be at the first dialer.
I also distinctly remember if you went to add a shortcut, you could use the "shortcut" option, not the applications option, and there would be a dialer. This is no longer there.
Lastly, is there any way to get the home key double tap function back in this rom? It is useful for linking to the dialer as well