As a Rounder in rainy Seattle, I thought I'd share what works for me. Pick and choose among my suggestions for what you think might work for you.
In order of effectiveness making cold/wet riding comfortable:
1. Pinlock anti-fog visor insert. Compared to some of the other items on this list, this provides the greatest cost/benefit ratio. Imagine being able to keep your face shield sealed closed all the time - even in wet, steamy, high-humidity conditions, with the rain on the outside of your helmet and you dry and comfy on the inside, with absolutely zero fogging of your visor! I've used a Pinlock equipped visor for 20,000 miles of year-round Seattle riding and can't possibly imagine riding without it. I went for the whole package - new visor with pre-drilled holes and the insert, but if you feel comfortable drilling holes in your face shield, you can just get the add-on insert without a new shield. It took just a minute or so to install and is maintenance free. HIGHLY RECOMMENDED!
2. Handlebar covers. Again, another piece of gear that is relatively inexpensive for the benefit it provides. Having an RT-P, of course I had to go with police-style handlebar covers custom built for RT-Ps out of a company in Oregon. Hippo-Hands are virtually identical in design and function. The only down-side is that they take a bit of time to get used to, and they block most of the view from the rear view mirrors. Since my bike also has a set of stalk mirrors, this isn't an issue for me. With the handlebar covers on (they install and can be removed in less than a minute), I simply don't need to use my insulated gloves. The heat generated by the grips stays inside the still air provided by the covers and provide plenty of warmth - even below freezing.
3. Waterproof armored suit. Now we're spending real money on products to keep you warm and dry! I wear an Aerostich. Is it perfect? No. Are there other brands with equivalent products? Of course. The point is to have an armored waterproof barrier between you and the cold wet stuff. Yesterday the temperature for the morning commute was 40 degrees, with light rain. I wore a t-shirt, jeans, and fleece jacket under my 'Stich and was completely comfortable. For the evening commute home, it was 50 degrees with light rain. Same clothes minus the fleece, which was stuffed in a sidecase. Plenty warm and dry. Many will complain that a 'Stich's zipper will let water in at a potentially embarrassing location. My solution is to simply layer a towel along the length of the zipper between my clothing and the 'Stich. Should any water leak through the zipper, the towel soaks it up instead of the crotch of my jeans. FWIW, I only experience water leaking through the zipper if I'm stuck in stop and go traffic in a downpour. If I'm moving through the rain instead of sitting in it, my windscreen and fairing keep most of the water off of me - which leads me to #4:
4. Larger windscreen/fairing. Now we have an opportunity to drop some real cash on either a larger windscreen or a new bike with a larger fairing. I have the largest screen Aeroflow makes on my RT. I'd rather push cold air and the rain drops over and around me than sit in a cold shower in a wind tunnel. But that's just how I roll. Also, I've noticed that from the waist down, the fairing on my RT (combined with the screen) I'm bone dry. The RT's fairing routes the rain around my legs, keeping them warm and dry.
5. Electric gear. Aside from my heated grips, I don't have any heated gear. Most of my Seattle rounder friends swear by their heated clothing, but I just haven't found the need for it. A fleece jacket under the 'Stich plus the grips + handlebar cover option is all the heat I need to stay warm and dry in nasty weather. Most around here use Gerbings, as it's a local company producing quality heated clothing.
Hopefully my experience and suggestions can help others in their pursuit of riding year-round in inclement weather.