My wife (a fine artist) liked the aesthetics and said it reminded her of a Mondrian painting, but she didn't get the lowercase 'a' or keystone :)
After your explanation, I do see the lowercase 'a'. But, it does bother me a little that the 'keystone' is rectangular vs. a wedge, as it seems like it might slip out of the arch.
I also see orthogonality and (as another poster said) a floppy disk.
Probably the most prominent image is a square which unfortunately doesn't seem very arc or arch like to me.
There seems to be a lot of potential with arcs, arches, 'A', lambda character, etc. Also, having a logo change is not a huge problem, so not getting paralyzed with an attempt to get the perfect logo initially is important IMO.