I experimented with a few things during the cross season. IMO the decision comes down to two things: How much money do you have/willing to spend? and/or how much can you tolerate the cold?
These combos worked in 35 below, some better than others.
Wool Socks and Regular shoes: I think the coldest I got these down to was 34 and windy. My feet were like ice blocks. This was not comfortable, although I managed to block out the frozen stumps attached to my pedals. I have various wool socks from woolie boolie to sock guy and heavy duty craft ski socks. Will not keep you dry (obviously)
Booties with Regular shoes: Provide much more insulation from the cold and from the wet elements, but not for to long. I have used chemical toe warmers which are great and will keep you toasty for hours but forget it if your feet get wet. On the road I have been out with my summer shoes, booties and toe warmers comfortably in 28-32* for up to four hours.
Winter Shoes: There are so many choices out there. I ride the shimano version. As Ben can attest to (I think hes tried them all on) sizing is an issue(pick a size that you can wear thick socks). Some are more bulky than other (ie LAKES) but offer probably the best product. Specialized, Answer, Sidi and Pearl Izumi offer versions as well.
My shimanos have kept my feet dry for the past two years. Not to long ago I was standing in ankle high freezing water and came out warm and dry.
The cold elements are something to get used to. Some guys and gals can tolerate the cold more than others. Your not going to be sitting in front of the fire toasty but you should be comfortable enough to get your ride in and not suffer to much.