Thanks for all the great responses - I'm glad they're still coming.
I went out on a friend's boat last night for the first of my many learn-from-sailing-with-other-people trips. Informal wednesday night racing (well, some people take it more seriously, as I learned from the shouting in other cockpits). Got a bit of an education in winches, spinnakers and race tactics while I was there.
I read through the syllabus Jackdale linked, and I was impressed enough to want to take some courses OR sail for a while with an instructor aboard my own boat. I haven't started researching particular instructors or organizations, because I have no intention of doing so until after I've purchased my own boat (one thing at a time, and I'm still spending time on OPBs to learn exactly what I'm looking for in my own boat).
It sounds like the largest issues people are bringing up are 1) tides and currents, 2) rules of the road 3) consequences of error. Another issue that is very pertinent to me personally is 4) deck gear on a mid-size boat. Now to address them in order:
1) I'm an oceanographer and a whitewater paddler. This means a few things. The less important facets are that I have a reasonable idea how and where tidal currents form, and have an excellent idea how boats handle in current (if it's got a keel, that can be summarized as "badly"). The more important facets are that I have HUGE respect for current (yes, I've seen the Skook wave, and I've canoed and kayaked on stuff like that, or bigger, a lot more than my grandmother would care to find out), also that I know where to find the tide and current tables for my area, and any area where I might be going. I will have those tables with me on board at all times, and I know how to read them. I've watched fibreglass boats shatter on rocks, and I've crawled out to stand on the rocks that wrecked them and wait for rescue. It wasn't fun, and I don't want it to happen again.
2) I know most of the rules of the road, and I know how complicated the other ones are. If I get into a situation in which I'm unsure, I'm more than willing to give way in the interests of safety, and make use of my radio (I've got that ticket already). More than Right of Way, however, I'm quite aware of the Right of Weight. I would never go and play with a freighter - it doesn't matter who's at fault, he's still gonna win. I use the same tactics riding my motorcycle.
3) Yes, the water is cold. No, I don't want to be in it. I've never been on hand to help rescue someone out there, but definitely listened to them on VHF 16. It's not fun, and I spent the whole time trying to dissect exactly what happened, why, and how I can not have it happen to me.
4) This is actually the point that is of most concern to me. I would have to and will spend a lot of time playing with the gear before I start sailing with it and working under load. It would be a slow process, likely starting with having only the main up and only going out in light winds, and gradually moving from sail to sail as my comfort level and skills increase. These are the skills that I'm most interested in improving in my little trips around the harbour. I also think that these are the skills that can get me into the most trouble (example: I'm sailing along, happily knowing exactly where I am, how fast I'm going, and what the tides are doing. I go for a tack, tangle a winch, get a bit stressed because my headsail is stuck in the wrong place, don't notice that my wheel torqued over a bit, veer towards the side of the channel, get into some stronger current, and then I'm on the rocks. Would the whole starts from a simple winch error. Of course, I could also have lost a finger or had some other mishap. The snowball effect is pretty common for disaster scenarios).
SeaLifeSailing - thanks for pointing that out about the commercial vs cruising certificates and the insurance companies. I hadn't considered that, and it makes a fair bit of sense.
Boat hunting around Victoria and the PNW