I have read this with interest. I started cycling this time last year, but with a hybrid with chain guard, and I was just wearing trackies.
Now on the road bike however, I am not sure what I should be wearing. Obviously there is nothing wrong with trackies, except they tend to flap around in the wind and I don't like the tuck into my sock look! According to the Garmin it was 11C today; I wore shorts, but with three top layers, on a 45 mile ride.
During the week though I did wear some "cycling trousers" (that's what aldi call them anyway, they're sort of tights but loose in the wrong areas?) when it dropped to 6C. I also have a pair of DHB bib tights, but I haven't had the courage to wear them yet: they're pretty tight in the legs at even a 41" waist (and I am a 36" waist).