Took a further look at this.
I'm pretty sure what the issue is (with it not looking so hot); it's using the "point" glow, instead of a really smooth gaussian glow, and the glow must get rendered first; after testing it appears that layer order matters (slightly). The main thing though is the texture needs to not end up ramping the additive up a lot at the center.
I tried it out with a 256 texture glow just to see it, and it looks pretty good, using Linear Dodge mode in Photoshop (acts the same as Additive + translucency in OpenGL), then did another test with a more typical-sized bolt and an outsized glow:


In this example, we have three layers that would be the quads, from lowest to highest: the red glow color, the red long trail (200% length and offset to match center) and the yellow projectile. The key to getting a reasonable look is that, since it's additive, the secondary color and glow should not be the bright color- inverting the RGB values results in some washed-out yellows and very little red.
A couple of very fast-fading copies of the yellow and the red trails would probably be enough to make it feel nice and wiggly, but it'd probably work better to break up the quads into, say, 16 quads along the length and wiggle them a bit each frame.
I think that that would actually get it done, because then the additive effects and falloff would be a lot smoother.
I've also found out the giving the shots length 0 still has weird effects, although it works while in flight; the secondary color shows up when the shot hits something, which looks really weird. So no glow, can't use length 0 (and any length > 0 means it's pretty much full length atm) and I tried out making one with inherent glow, but that bug kind of was a show-stopper for now

Anyhow, sorry if all of this is kind of lame carping about minor detail stuff; I just wanted to explore the issue a bit and see if there was anything simple that could make it work better
