I'm on a high Spiro and low E right now (hopefully more E by end of month).
As far as I can tell the following have happened:
Sensitivity and development of breasts (I already had these; now they hurt a lot more)
Smooth skin, I think (never compared to aught)
Increase of hair growth in male-hairline areas
Decreased, less spontaneous libido
Change to, umm... Output...
So, unless I'm responding really well to low-dose E, those are a good number of demonstrable effects.
It's a case by case basis, though. Pretty sure my T levels have always been abnormally low (my endo doesn't test 'cause it's Wisconsin and nobody covers it, but there you go), so the Spiro probably had a better than average effect.