I will definitely be restoring it as funds, time, and luck allow.. I've even kicked around the idea of doing Tempest in JAMMA for now (if that's possible), just to bring it back to life without having to completely gut the thing all at once.
I don't know how you feel about MAME, but here is what I did with the empty Tempest cabinet that I picked up from Al Warner:
$100 for the cabinet, all artwork was intact and CP, spinner, and buttons were there. Installed an old used SVGA arcade monitor (bolted right in), used a PC with MAME, hacked a PS/2 mouse for the spinner and hacked a USB mouse for the buttons. So I had a playable Tempest for about $250.
The old SVGA monitor died so I replaced with a brand new Betson Tri sync and ran Tempest at 640x480 form the PC. Also loaded Tempest Tubes, Tac Scan, and Arkanoid.
So now for about $500, I have a nice, completely original-looking Tempest that plays Tempest, TTubes, Tac Scan, and Arkanoid, and is not plagued by the unreliability of original Tempest hardware.
Yeah, I know, it's not a vector monitor, but it still looks awesome, and I don't have to hold my breath everytime I turn it on...
Of course, if you go this route, you will still spend a buttload of $$$ because you will need to get artwork, CP, etc.
Still, something to consider.