Hi I live in the SW UK, where it rarely gets cold but does tend to be pretty wet and windy.
Until a couple of years ago I was going with the fleece and pertex approach, this worked well for me until in July 2010 I was walking accross Dartmoor in heavy rain and strong winds. The temperature was about 50oF, but the 40-50mph winds made it feel much colder. The wind was driving the cold rain strait though 2 pertex layers (a Montane featherlight and lightspeed jackets) a micro fleeca and a baselayer and onto my skin. Whilst hiking (fast) I was just cold, but as soon as I stopped I started shivering uncontrolably and could therefore not stop and rest or eat. I was very concerned that if things got worse or if I could not continue I would be in serious trouble.
After that experience I bought a Montane lightspeed H20 jacket http://www.montane.co.uk/products/men/shell/lite-speed-h2o-jacket/164 and a cheap pair of waterproof trousers http://www.mountainwarehouse.com/mens/clothing/waterproof-trousers/pakka-overtrousers-p2629.aspx?cl=NAVY. I have twice since been out in poor conditions using these new items and have found they make an incredible difference.
The first occasion was in August last year, the rain was heavy and the wind was moderate, nothing like the year before, but I would have been soaked to the skin in fleece and pile. I wore just a base layer under the water proofs and although wet with perspiration I was comfortable, I think the big difference wa that I was being soaked by warm sweat, not cold rain. When I stopped and put up my tent I put on a fleece layer over my base layer (having taken off the waterproofs)and they were dry very quickly.
The second occasion was in January when I was hiking in 40 mph winds at 40oF with a mixture of rain sleet and hail, again I wore just a base layer and the waterproofs. I was just cooler than comfortable, but experienced no humidity inside the waterproofs. When I stopped for a break, I put on a snugpack jacket http://www.snugpak.com/index.php?MenuID=93-104&ItemID=101 with a cheap water proof http://www.snugpak.com/index.php?MenuID=93-104&ItemID=101 over the top. With this on I was comfortable even when sitting around for a half hour break.
The Lightspeed H20 is not very breathable MVTR or 6,000g/m²/24hrs. Montane have just brought out a new jacket http://www.montane.co.uk/products/men/shell/minimus-jacket/412 using Pertex sheild plus which is much more breathable MVTR of 25,000g/m²/25hrs. It would be interesting to see how much difference this would make in the warmer conditions. I am convinced that if cool enough, the best way to avoid moisture inside your shell is just to make sure you don't sweat by controlling your temperature! When my light speed wears out, I will try a more breathable jacket, but for now am happy with my system.
With regard to other equipment I have found that my down quilt is great if the weather is dry, or if you are only out for one night, but if it is wet and you are out for a number of nights, I find it looses loft and warmth. I am going to be making myself a climashield quilt for this winter.
At the moment I use a Tarptent squall, which I have had for nearly 10 years. I have found it to be a great shelter. It has stood up to winds which I would never have guessed it would when I bought it. The only issue I have with it is that it is a bit of a wind tunnel, and this makes it a bit of a chilly place to be in a storm. I am thinking of either some sort of mid shelter or TT Notch or Stratosphere for it's replacement.
I have never used buffalo clothing, but had one of their bags years ago. The bag did not wrk for me, and although the clothing sounds like a great idea, I have never met anyone who uses it in a backpacking situation.
Paramo clothing has a very loyal following over here, but most find it too warm to wear outside of winter, and you have to be very fastidious with keeping the DWR in good condition otherwise it looses its waterproof qualities.
Hope that was of interrest!