I also highly recommend the freezer suit as observing attire.
See
http://www.hepworths.com.au/
See
http://www.gtbastrowise.com.au
Before the freezer suit, I also use to use the layered approach including
thermals.
A small fraternity of observing friends began using the freezer suits quite some time
ago. They extolled their virtues to the rest of us and there were many a freezing
night when the rest of us would start to feel the cold and begin to fade when those
with the freezer suits kept perfectly warm indefinitely.
Then a couple of these friends bought us freezer suits as a gift one year and
we never looked back.
With a one piece freezer suit, it is not uncommon for many of us to then simply
have nothing underneath it except some shorts and a T-shirt even in sub-zero
temperatures. Only a few years ago at one of the South Pacific Star Parties
when it got cold, I remember chatting to some who had as many as eight layers
of clothing on yet still reported feeling cold. They were shocked, as their teeth
chattered, to learn that those wearing the freezer suits were not only comfortably
warm, but could pull down the zip to reveal just a thin T-shirt beneath.
The other advantage the suits have is that they are very fast to don and doff.
When most freezer suit owners turn up at an observing site these days, they
often begin the night by removing some clothes first before climbing into the
suit - the opposite to the layered approach.
Women often find the two-piece suits more convenient but they are not quite
as warm as the one-piece suits.
Certainly up here in Sydney with the ASNSW fraternity, most of the
experienced observers are the ones wearing the freezer suits but since Geoff
began distributing them at the star parties, they have become ubiquitous
among new observers as well.
Best Regards
Gary Kopff
Mt Kuring-Gai
it not cold down here in the Valley, 
or Ballarat for that matter. 
and it keeps me nice and warm.
it is a wonder you can move at all with that kit on. 
