+1 to Rasterman on all of that info. He's right, with the projector housing already done, you can get your vehicle close to factory-looking HID equipped cars. Close.
I went about the whole process wrong when I upgraded to HID's in my 2007 Outback. I went for the cheapest kit available....such as the one on simplyhidkits.com (owner/parent company is Kasa Stores.) DO NOT FALL FOR THIS SCHEME. The kits are absolute dirt. Makes sense - I think I paid $105 total.
After haggling with that last company, I stepped up in my price-point; For $170 + shipping, I got a complete kit through carhidkits.com. I got the 6000k color (bright white), digital slim ballasts (highly recommended), and the extra wiring harness (highly, highly recommended.) Each component is explained below...
The color I chose - 6000k - most accurately represents natural sunlight. I would say these are about 95% as bright as stock HID's (2006 Lexus GS 430 is a tad brighter, as well as some of the Audi's and a VW Toureg I matched them up with.) Honestly, there isn't enough of a difference where the untrained eye will notice. If you get another color, IMHO you probably run the risk of less visibility. If you are upgrading the lights for better visibility, I would stick with 6000K on the main projectors. If you went with yellow (I think 4500K-ish is yellow) for your fogs, then I think you'd still be happy because the 6000k's will do their job - illuminate brilliantly.
The digital slim ballasts ($20 extra) are a godsend for our engine compartment, because of the lack of good, flat mounting space. The larger ballasts would not have fit in the spaces I currently have the slim ballasts. But these ballasts aren't a good buy simply because of size - the digital part is importanat. This is where I get a little fuzzy (and where you should start Googling), but to my understanding, the digital signal is a much more clean power signal to your lights. Non-digital ballasts can sometimes cause tiny surges, giving you the "flickering" effect that so many HID customers complain about. With the digital ballasts, this flickering is completely eliminated.
The extra harness I talked about (another $20) is so that both your passenger and driver's side bulbs turn on when you start the car....(disclaimer: I'll try to not lose you in the explanation here, but sorry if I'm not very concise. The numbers are not important, but the overall concept is.) HID's use something like 60% more power to turn on your lights (on initial startup, due to the fact that it is a gas, not filament), and use 35% less power while the car is running (as compated to filament-style bulbs.) How the kit is made (as is every other kit on the market) is that the power runs from the battery (as the power source,) through your driver's side light, on to your passenger side light. Without this harness I recommend getting, when you start up the car (with the HID kit installed, minus the harness), your passenger bulb will come on only 50% of the time. That means you would have to turn the car off, then turn it back on, and possibly do this a few time. So simply put, all this harness does is provide an extra power line running from your passenger side bulb to the battery, and also provides an extra ground. Do yourself a favor and buy that harness with the kit.
The install (if doing yourself) is not hard. I'd say the hard part is keeping the stock look of the car - which I wasn't able to do, but got very close. The wires are routed so that they're almost hidden. A trained eye would know what they're looking at, but the average Joe/Jane would not know the difference. My point is that with this kit, it is possible to get very close to a stock look. If you spliced in a foot of wire in a few of the wires, you absolutely can achieve a stock look, but the length is what is limiting this kit.
As for operation, I've had mine for a year, and nary a problem. 100% of the time, they work EVERY time...haha (not sure if you caught the Anchorman quote there...) I've had probably 4 or 5 friends, some of them mechanics, that ask if my car came stock with HID's. (Meaning, they are a good product!) One gripe about the operation (versus a stock system) is that if you turn off the headlights, they will not strike back on. Might sound like a big deal, but with our headlights coming on automatically, you probably don't manually turn your headlights on and off often, or at all. In that case, you would have to turn off your car, then turn it back on with the headlights in the "on" position. Again, its a small gripe because I never manually turn off/on my lights.
Lastly, I have not done the DRL disable yet, and I may never do it. All you have to do is clip one blue wire under your dash, easily accessible. This literally takes one minute to do.
One thing I forgot to mention was this: consider going LED for your fog lights. I've seen it done very cleanly, and for very cheap. Don't go SUPER cheapo, like the $6 bulbs on Amazon. But there are other ones for $28 - $40 on the net that have had good reviews...(MUCH cheaper than a 2nd HID kit.)
All in all, its a good experience. Even if you don't go with this kit, take this information to another manufacturer that you're considering. If you have other questions, fire away. Good luckon your purchase!