I'm in the New Hampshire National Guard and (until last year) I was an avid hiker. I have spent many hours outdoors in NH and MA, including overnights during the deepest winter. I also worked security outdoors third shift last winter.
I prefer the ECWCS parka plus Polarfleece to the M65. I have worn both extensively and the parka/Polarfleece combo has significant advantages over the M65. However, I did not pay for them (and I'll be sad to give them back) and so I shelled out $100 for a North Face parka and a EMS fleece with the same features for use on my own time.
There are some very bad ECWCS parka copies out there. I have inspected one type at the Salem, MA Army/Navy store. I highly recommend you make sure that you get one that is military issue (not just GI-spec). If this makes it too expensive, the M65 is a viable alternative. It is more likely that the M65 you buy will be either military-issue or a quality copy.
The parka has roomy velcro pockets, pit-zips, a much better hood, and is lined with Gore-Tex. The Polarfleece jacket also has pit-zips. The parka's chest pockets are perfect for carrying a pistol for quick access if open carry isn't an option.
The M65 is water-resistant but it will soak through if you spend several hours in heavy rain. The issue liners are not very good IMO and you're much better off with a Polarfleece to serve the same purpose. It also gives you more layering options, and the issue liners are useless on their own (no pockets or front zipper). The M65 hoods are not waterproof or lined, and they look incredibly stupid. A waterproof hat will become necessary if you choose the M65. I wear a olive-drab M65 on occassion but only as a casual work jacket.
The most important feature other than Gore-Tex, IMO, are pit-zips. They allow you to cool your core down quickly without stopping to shed layers. Ideally your first layer will have them, too, so you can get cold air all the way down to your longjohns.
For most conditions, I find I need only three layers: Polypro longjohns, Polarfleece jacket, water-resistant pants, and my North Face parka. In my pack or at the camp I have a goose-down vest, water-proof pants, and Polarfleece pants. I also have two thicknesses of gloves, a wool watch cap, and a Balaclava. When out with the National Guard during winter we have much, much more than even that, including a three-bag sleep system, "Mickey Mouse" insulated boots, et cetera.
My Poor Man's outfit would consist of the following:
Lighty-used M65 Jacket
Polarfleece knock-off
Polypro underwear
Wool watch cap
Military-issue poncho for waterproofing yourself
Waterproof gloves that can accomodate liners
Wool blend hiking socks
In your pack:
Extra socks
Goose-down vest
Poncho liner aka Woobie
Synthetic balaclava