I evaluated it briefly, but didn't then start using it because the VHDL
cababilities were a bit inferior.
Yes, some of the Alliance tools use GUI (not all). If I remember correctly,
there was at least silicon layout editor that was graphical. But I don't think
that is very useful in practical work, most people are using VHDL synthesis
programs that directly generate the layout.
Alliance directs users first to describe logic behaviour with very simplified
VHDL syntax. Then the layout is created by hand and the netlist is generated
from it.
The netlist is compared to the behavioral description to see if they match, but
since one can't generated automatically from the other, it's double work which
I don't find making much sense.
My description might not be completely accurate, since it's long time ago I
tried it, so correct me if I have mistaken.
You should also try out "Electric".
http://www.staticfreesoft.com
I found this much more easier to use and useful, although it doesn't
support much VHDL either (just very simple netlist syntax).
Coding VHDL textually is, by the way, much more powerful than using
graphical CAD tools.