Rode a 43F'er yesterday:
*got both for $120 = check out Gottaridebikes.com and use their 20% coupon for your first order
+
Pearl Izumi knee warmers (fleece lined)
Under Armour Cold Gear turtle neck
Under Armour Extreme Cold running Gloves
Reg cycling shorts + reg socks
I was overdressed. I'd still be toasty with some Heat Gear UA turtle neck + regular full finger gloves (I'd keep my shoe covers though since I hate when my toes are cold).
If it was 10F less then I'd probably throw in an extra beanie underneath my helmet to keep my noggin' warm.
PS
some chic passed me and she was just wearing a hoody + knickers. I was semi-embarassed