Well, I have some pretty extensive experience in this area so I'll clear up some of the things that I have seen in this thread.
First off, all bulb type kits are not equal. Most folks get theirs off eBay and you'll find everything from lousy to quality type kits offered. One thing that I have noticed is that you get what you pay for. Every guy who I have seen complaining about their lights doing something funky after applying the known fixes always took the cheaper route, searching eBay for the lowest possible price they could find. The vendor I bought my lights from dropped his prices some but they have held steady for over a year now. That pretty much tells me where his profit margin is and that he wasn't going to go in the hole trying to match prices with guys selling HID garbage.
Another thing that I noticed was that the better kits always had German ballast. Apparently, the Germans have this figured out and the quality of their ballast show. Those with ballast made in China and Taiwan seem to always be having issues. Like I said, you get what you pay for.
I had the bulb type HID's up to a few days ago. I ended up installing a powered harness (bypassing the stock wiring) in order to eliminate the issue with my buckets not raising the first time I turned on the lights. This totally remedied that problem. I then remedied the problem where the lights would go off when I turned them off but the buckets would on occasion stay up. That was what the resistor was for, however, I used a 194 bulb to solve my issue.
Since folks did not understand what was causing the lights to act differently than stock, they had a hard time understanding how to fix it. Here's the whole problem in a nutshell.
The C5 headlight circuit is a 55w circuit. The ballast used with the bulb type setups are 35 watts. This drop in wattage is what caused the buckets to perform abnormal. Since my degree is in Electronic Engineering Technology, I knew that I could increase the total wattage of my headlight circuit by increasing the voltage drop withing my headlight circuit. All headlight circuits are parallel circuits and voltage adds in parallel. Since voltage times current equals power (VxI=P), creating another voltage drop in parallel with the circuit caused the wattage of the circuit to raise, which also increased total circuit power and eliminated my bucket issues.
Now that I understand how the circuit works, I should have just bought 55W ballast and that would have eliminated my issues too, but hindsight is 20/20.
With all that said, here's are two videos of me rolling down the freeway with my HID's on (actually, my girlfriend is driving and drifting all over the lane :ugh). Notice how everyone else headlights dissolve when they enter my headlight beam. The second video shows me
changing from my stock HIGH beams to my low beam HID's. As you will see, the difference is phenomenal. They are more than worth doing the upgrade and they are 20 times brighter than going with those Sylvania HID bulbs. Those things are a joke compared to ballast HID's (contrary to what was posted earlier in this thread). In this picture, you can see how the passenger's side HID upgrade is significantly brighter than the driver's side stock headlight.
Here are both videos:
Low Beam HID's on the Freeway
Stock HIGH Beams to HID Low Beams
Now with all that said, know that this setup is illegal in every state in the US. You cannot by law use a HID bulb in a non-HID enclosure. The C5 fog lights are actually HID enclosures and thus, this upgrade is totally legal there but NOT in the stock C5 headlight housings. Also, if you aim the lights properly, you will not blind oncoming traffic. Some guys don't bother to do this and give the rest of us a bad name. There's also the aiming mechanism with the C5 that if not freed before it is adjusted, will snap in half and make aiming impossible. This is the problem that a lot of guys experience and is why so many people are driving around blinding oncoming traffic.
Fast forward to today. I have finally decided to go with a true HID setup. It was not cheap ($1100). These are the light cannons with city lights (halos). One look at them shows why they are so expensive. This setup was designed by a fellow Corvette enthusiast I know and was designed from the ground up by him. These are not fixed headlights, they will still be popups.
These are really sweet and are going to throw off even more light than I had. The ballast are 55W and of course, made in Germany. I'm working on the install as you read this.
Check out this mess of wires... :ugh
So, I will finally be legal but I had nothing but a positive experience with my former setup. It really all boils down to, "you get what you pay for."