Terry nobody told me this starting out - if they had it's likely I would not have listened to them when I was in my 20's. After years of biking, primitive backpacking, hunting, & boating & back to motorcycling, the gear makes a lousy weather day into a tolerable experience or even fun. As you say, it can serve multiple purposes & even though it's expensive up front, the comfort & service outweighs the expense very quickly.
Copper Black - I have $700-$800 invested in Gore-Tex rain gear for my wife & I. Sounds nutty maybe. If you get Gore-Tex or equivalent, you may find it for a little less, but make sure its seam sealed & as 2LaneRider posted - practice trying it home first & on the road BEFORE it rains. I'm bad about that myself - riding into the rain & doing the old huh-oh.........
That's about what I've got tied up in rain gear...Arc'Terex (sp?) Gore Tex bib type pants w/suspenders...zip all the way down both legs, so easy to get on and off. They are ski/backpacking pants, so totally seal around the boot and have a heavier piece of material on the inside portion where it goes over the boot for abrasion resisitance, and an inner gaiter to keep the snow/rain from getting up the pant leg (good for forward controls on a bike, but designed for snow). I have a HD Gore Tex pac lite jacket. Once the pants get put on for the day, they generally stay on, as they are quite comfortable and do not give you that "clammy" feeling because they are Gore Tex. On weekends, I often use Bank drive thrus to put the gear on...even small towns have them if you can't find some other covered place to put gear on. We keep both rain suits in a nice waterproof Outdoor Research stuff sac, and I keep that easily accessible so I can just grab the stuff sack without digging around...on longer trips, when saddlebags are full of clothing/tools, the stuff sack gets bungied on top of the TP so it's literally a couple of seconds to get it off and pull the gear out.
Ski shops are a good source for this type of gear, and at certain times of year, you can find good sales. Don't forget some kind of waterproof glove...I have a pair of waterproof/breathable shells that go over my thinner deerskin gloves, or can be worn alone. I have another pair of canoeing gloves that are like wet suit material...precurved, so they work well with the grips, and have the added benefit of warmth plus waterproofness.
It's an investment up front, but can turn what would othewise be a miserable experience into one that is at least tolerable. Most of us wear cotton clothing, and once cotton gets wet, it is miserable to stay in for the rest of the day and takes forever to dry. I like the wicking type t-shirts/long sleeved shirts...no, they don't have HD written all over them, but they keep you cool/warm and dry extremely fast if wet or sweaty.