Schecter has some too, but they're limited edition for 2009. One is based off their C series, and the other is a V.
And ESP makes an LTD one aside from the pricey Stephen Carpenter sig.
8-Strings are also actually used by some Jazz guitarists, like Charlie Hunter. Though his is quite a bit different as you can see below, having fanned frets and 3 actual bass strings over 5 normal ones.
http://www.youtube.com/watch?v=-B7btsk6ASE
My only real problem with them, aside from being cumbersome, is that the 8th string pushes the guitar's tonal range even further into the side of the mix that the bass handles. So when you have a full band going, you really won't be able to hear it that well, especially in a live setting. Even more so if you're playing a passage that's more intense and "busy", musically.
Yeah i can see what your problem with them are, but i wont be using it in such a fashion, just because i have 8 strings doesnt mean i have to use the bottom two at all times, i'll be using those when i musically feel i need to, passages, bridges, stuff like that, but as i will be mixing myself im going to find a way to bring the guitar forth in one way or another, haha.
The LTD one is shit and i wouldnt buy it at all, its got a fucking 25.5 inch scale! Thats not nearly enough for a 8 string, those strings are gonna be sloppy and hard to intonate, not for me. I dont know what Schecter works with, with their 8 strings, but man that V was butt ugly..