Ok, I'll start by addressing the power issue.
Even though HID buners consume 35 watts...that'* after the initial startup, when they've come up to temperature. When you first turn them on, they need a surge of current to fire the burners. That'* why you should always run a separate wiring harness that uses 14-16 gauge wire, and a relay, with the power coming straight from the battery. Those harnesses are usually under $50, and the plus side, is they'll usually make your regular headlights brighter, too (depending on the state of your current wiring, and how your vehicle routes power from the battery, to the fuse block, to the headlight switch, to the headlights).
So, always use a wiring harness unless you're sure of the capabilities of your current wiring.
Second, I'll get some terminology correct.... A "kit" is when you buy one of those cheap asian HID systems that is meant to fit into a halogen housing. 9006 (low), 9005 (high), H4, 9007, H1, H3, etc.
A "retro" or "retrofit" is when you take a set of real HID projectors (or even a reflector setup, but nobody does that due to the complexity, and the fact that projectors put out more and better light due to their increased effeciency) and hack apart your current headlight housings and install them into the housings. It'* be best way to go about getting real HID without blinding people, and, maintain the correct photometric parameters to keep your vehicle projecting a legal field of light. The only thing not legal about a retrofit, as far as I can tell, is you're not going to have the correct stampings on the headlight lens. Minor issue.
Quality of parts. Any of these "kits" you see on ebay from china, korea, hong kong, whatever are kinda hit and miss. You may get one that lasts forever, you may get one that lasts as long as the typical pop song on top 40 radio.
Philips, Hella, & Denso are three OEM manufacturers of ballasts that I can think of off the top of my head. Philips and Sylvania are the two popular burner manufacturers. Yea, you can't get a complete OEM setup for $150, probably double that, but you'll have something that should last you the lifetime of your vehicle. I don't think a lot of people put upwards of 3000 hours in the drivers seat (well, i might, but that'* another story).
Why a "kit" is no good. The stock headlights on most american vehicles (and some imports) generally leave a bit to be desired. This is especially true of 80'* and 90'* vehicles. Even my 94 bronco'* headlights were "ok" but not great. Mainly due to the DOT regulations that specified beam pattern, and no maximum upward light scatter. I found out that both ECE (E-code, european specs for automotive stuff) and DOT specify a minimum amount of upward light scatter, but ECE caps it at a maximum, DOT does not.
The beam pattern of an ECE system is usually better, with a sharper cutoff for the low beam, and more of a "flood" pattern, than a "spot with some flood" pattern. Now that cars are becoming more global, the headlights are becoming a "homoganized" type, with characteristics of both ECE and DOT in them, and they pass spec in both areas of the world. Nearest I can figure, my Jeep'* factory lights are like that. Can't really find any ECE headlights for it, only the ZJ'* (93-9
When you throw a HID kit into a halogen housing, two things happen. 1. The amount of light increases by 3-4x. So, if you had say 200 lumens of upward light scatter with a 1000 lumen bulb, you now have about 600 lumens of upward light scatter with a 3200 lumen burner. (Eh, roughly.) 2. Also, the size and shape of the arc is different than the glow from the filament. The position of the arc in the housing also may be slightly (or radically) different. I found that the cheapo 9006 burners I have, produce the EXACT same beam pattern as the 9006 halogen bulbs. Both in a set of aftermarket "jdm" "euro" "blah" housings for my Jeep (which have a surprisingly good cutoff), and Bandit'* bonne headlights. His lights did produce a crapload of glare. These burners had no masking on them to block excess light scatter, either. Masking may help, but it'* not a long term solution. You may be able to find a halogen headlight housing that has very good optics that will direct a properly rebased (or manufactured) HID burner'* output just to the ground, and not scatter it upward, but it'd be cheaper and easier to do a retrofit, since changing whole housings to a different style housings is damn near impossible (I mean radically different, not just a 92-95 to 96-99 bonne headlight swap, probably get similar results with that).
Then you have to look at foreground lighting. How much light is dumped directly on the ground in front of the vehicle? My "kit" didn't do too bad, but the light pattern was only slightly brighter at the top (far end) of the beam compared to the bottom (near end) of the beam. That was in the reflector housings. It dumped a lot of light on the road closer to the vehicle. Yea, looked nice and bright! Problem: didn't help me see further down the road.
My projectors put the most light out at the cutoff line. That is WAY down the road, the closer you get to the vehicle, the less light hits the road. They look dimmer than my reflectors. Really! But, I found that i can see better because my eyes weren't being blasted with all this close foreground light. The amount of light down the road and to the sides was much better.
Here'* a low beam comparison:
HID "Kit" in my 9006 aftermarket housings:
Bosh E46 projector retrofit:
Hm.. even the kit doesn't look that bad, but the light is more splotchy, and there are hotspots in the beam. An even, uniform lighting is easier on the eyes, and tends to not draw attention to any one part of the pattern. The pictures don't really do it justice, though. They were on two different roads, with two different cameras. The color temp of both of those are about the same, the 9006'* were 4300K, the D2S burners were 4100K.
Damn, I need a new camera.
Anyhoo, there'* my $.02 on the whole HID thing. (What a bargain!)
BTW, the lights in my avatar are the aftermarket reflectors, obviously, that was before I put the projectors back in.