Adrian. The 'perfect room' would be [bilatterally] symetrical with a mix of absorbtive and diffusive characteristics.
Drywall over studs will act as a resonant absorber at certain frequencies, depending on the density of the drywall and debth of the cavity, and reflective at higher frequencies (say above 500Hz to 1KHz).
Glass would be transparent at low frequencies (resonates and allows low frequencies to be pased through because it is not covering an enclosed space [resonant absorber]) and reflective at high frequencies.
Having differences from one side to the other
may have a noticable affect in imaging. As and example, the couch I have along the left wall blocking part of my left speaker shifted the whole soundstage noticably right. I had to boost my left speaker by about 2db to center the image, and I suspect it still affects the 'placement' of instruments on the soundstage.
Probably the main reason I am aware of some of the defficiencies of my room is that I had the chance to audition the system I bought in a symmetrical and acoustically good room at Axiom.
I was wowed by the difference between two channel and 5.1 music on one of the live discs I took with me to demo. I do not get that same wow difference in my room. Had I never listened in such a good room, I would probably be ignorant of the shortcomings of my room. [As a side note, I wonder how many people are underwhelmed by 5.1 music because of less than good/perfect acoustics in their room.]
Being a perfectionist/pedant, I now feel bound to chase acousic perection. Being free of WAF, that could be dangerous.
Having babbled all that, if you don't notice anything wrong with your room, don't worry about it too much.
