Does anyone have experience with any of the 3rd party lighting kit companies for sets? Do you have any information or stories about how these lighting kits work out in practice? These are the two companies I am looking at:
BrickStuff is very high quality, I have used them many times. They are US based, make all their light kits with thought and care, and stand behind their products. I especially like that their lights can be controlled for various light-effects and intensities. Flickering soft lights for candles and fireplaces, bright pulsating lights for emergency vehicles, etc. They are, however, expensive.
I'm not familiar with the other company, but it seems like they are just resellers of the light kits made by Chinese companies and resold by a number of websites (BrickLoot.com is another one that I'm aware of selling these kits, but there are others as well). I do have some samples of these products, and they are okay. Not as good as BrickStuff, but more affordable. By "not as good" I mean that the components are not as high quality, and the connections are often not as clean and nicely finished as with BrickStuff products. You also get a lot smaller variety of lights and effects. But they do work, and are usually cheaper than BrickStuff.
Whatever light kit you end up using, be prepared to be running lots of very tiny and delicate wires. This makes the interior spaces of the buildings/vehicles (where you will be hiding the wires) less attractive and less usable. BrickStuff does have some suggestions of minimizing the visibility of unsightly wires, but ultimately, they can't be avoided.
Having all those wires running also makes the models hard to play with. For example, if you install light kits in the LEGO Modular Buildings, lifting off the floors is going to be tedious. The wires are also delicate, so you want to be careful around them so they don't get damaged. Light kits with wires work best with display models that won't be moved around.
While personally I prefer BrickStuff when it comes to wired light kits, I haven't fully committed to them, as I like to keep my displays modular and accessible for play, display, and modification. Currently, I'm waiting for the release of i-Brix.com products. These are wireless lights for LEGO that work with the same technology as wireless chargers for electronics. The system includes a special transmitting surface that you can place under baseplates, road-plates, etc., and any i-Bricks lights you use over this surface will automatically light up. There are no wires between lights, or the lights and the power source.
I-Brix had a successful Indiegogo campaign a couple of years ago, and they are getting ready for release of the first batch of their products sometime soon. Check their website for updates. I think the combination of wired light kits for stationary displays with various interesting light effects, and wireless lights for moving and more dynamic displays is going to be an excellent combination.