I'll take a stab at some of these questions with MY opinion…
Self launching and landing is definitely an advanced move which you should only do after you've got regular launches and landings dialed. Launching and landing is (in my opinion) the time when things can get most out of hand - you've got hard objects around you and less room for mistakes. Only practice self launching and landing in areas where you won't hurt anyone or yourself if you make a mistake. Big beach areas are good - Ocean Beach, Waddell, etc.,I know that self launching and landing are things to be avoided if possible. How big of a pain is it? Is self landing hard on the kite?
Here's a video from Caution kites on self landing:
http://www.cautionkites.com/vid/vid.index.tut.sland.php
Notice what he says about grabbing the upper power line to land the kite. Some kite/bar setups have a single front/power line which runs through the bar and then splits somewhere up the front lines. This would make grabbing the top front line impossible. I'm not sure how you'd go about self landing a kite with this setup. If self landing is important to you, it's a good thing to mention when you start looking to buy your kites.
Self launching and landing can be a bit more rough on your gear as there is a tendency for the kite to slide along whatever surface you're launching/landing on. If it's sand, no worries. If it's a parking lot, expect a bit more wear on your gear.
I'll plug the Slingshot Rally as a kite which is really easy to self launch and land.
I own 3 kites - 6m, 8m and 10m. It's pretty rare that I'll blow up more than one kite for a particular session.I've read great things about the wind range of modern kites. I'm looking forward to that because I hate re-rigging as a windsurfer. How often does re-rigging happen when you're kiting? How accurate would you say this wind chart for kiteboarding is?
You could probably get away with one twin-tip board, but you'll eventually get the bug for the surf/carve thing and want a directional/surfboard. One nice thing about a surfboard is the additional flotation for lighter wind days. Or with the additional float/length, you can use a smaller kite which turns faster (more fun).How many kites/boards would you consider a complete quiver if you're just on the bay and not doing waves? Does it make a difference?
I haven't found this to be a problem. Kiteboards are much smaller than sailboards and therefore tend to 'go with' you when you fall, rather than twist up your parts.I was always a little concerned about getting my foot caught in a footstrap when windsurfing if I had to bail out. Is that ever a factor in kiteboarding?
If you had a choice of being over powered or under powered on a kite what's preferable? Is sine-ing or running the kite in figure 8's a pain if you're underpowered or something you do routinely?
Modern kites have a pretty big wind range and lots of depower. It may not be obvious to a non-kiter, but you can trim the kite to adjust the power *while you're riding*. Therefore, if you chose a reasonable size kite when you went out (ask people on the beach if you're unsure), it's pretty rare that you'd be dangerously overpowered, unless the wind speed increased significantly while you were out.
If needed, you can generate buckets of power by doing s-turns and/or kite loops.
I hated slogging on a windsurfer too. The kite is 65+ feet away from you and generates an insane amount of power when turned or looped. Nothing even close to a 'pumped' windsurfing sail. You spend less time slogging kiting because you can make so much power turning the kite.I hate slogging on a windsurfer waiting for enough wind or a gust so I could get up on a plane. Is there such a thing as slogging on a kiteboard or are you just sitting with your butt in the water trying to waterstart?
There is pretty much only one place to launch/land to kite in the Berkeley Marina area. The launch isn't for beginners and/or the faint of heart. At high tide, there is pretty much only iceplant to rig, launch and land on. That plus there isn't' any room for a mistake when you initially leave the beach. A while back someone on this forum asked about the launch. Here's what I said then:I windsurf mainly at Berkeley marina and noticed that on days that I thought would be good for kiting I'd see no one out. Then when I thought it was marginal I'd see several. What are the factors there that would affect that? Tide? Steady/gusty?
"The spit at Pt. Emery is a bit of a tricky launch, especially at higher tides. Immediately to the North of the launch is a rocky outcropping you have to get upwind of. It's pretty much send the kite, edge and ride upwind. There isn't much time for anything else on the very first tack.
In addition, when you send your kite that first time, it will be VERY near if not over the frontage road, where there is plenty of car, bike and pedestrian traffic.
If that's not bad enough, Hwy 80 is another few hundred feet downwind. If you had to punch out, it could get really ugly with kites and lines combing with vehicles at high speeds."
Here's a diagram of the launch:

and a discussion we had previously about the launch:
viewtopic.php?f=1&t=8810&p=58813#p58782
As for why you're seeing kites sometimes and not others, I'd guess it's because there is a pretty small crew of kiters who ride there regularly.
Good questions. Keep 'em coming!
Kirk out