Re: Chris' eigertek points--
i) Different boxes handle this different ways-- some (like the Eigertek) force you to have a working body cord and weapon (which you're supposed to have anyway

). The SG series boxes can still register a valid light if the BC ground is bad, but will keep beeping at you as long as the white light is on (unless you turn off the sound). Some just leave the light on and don't sound off about it after it first occurs.
ii) That's a self-test mode that the newer Eigerteks have-- power it up while holding the selector button down and it'll cycle through the test routine to show if all of the lights and sound are working.
For the hits on the blade registering, this means that there's some leakage between the A-line (lame/mask) and the C or B lines (weapon) on the receiving fencer's end. Could be an uninsulated part of the weapon contacting the lame directly or via a sweat-bridge, or a momentary short in the body cord (hint: the vast majority of flaky problems end up being body cord related). See if the yellow lights are flickering on-- this indicates that there's an A-C short. As for the light not registering, remember that there still is a whipover lockout in sabre-- if you're at all contacting your opponents weapon when making your not-fully-closed-out touch, that blade contact will trigger the whipover timer. There is a tolerance for the acceptance and rejection times for whipovers in the FIE spec, so some machine designs can let fewer whipovers through than others but still be within regs (and if your game is highly dependent on landing those marginal whipover shots, well then...

).
My advice: keep your body cords in good working order and go with the Eigertek-- we've been quite satisfied with ours for foil and sabre, and it just can't be touched for the price. Another plus of the Eigertek is that it runs just dandy on a 9V battery, if you're going to be using it where an outlet isn't acessible.
There are two other boxes in the Eigertek's price range: the Favero FA-01 ($350 for hard-wire wall mount, $400 for the "table" model that takes normal floor cords), and the Amico RS-01 (that's the $375 'pocket' machine sold by Blade). The Favero is much bulkier than the Eigertek, and the case isn't as sturdy, but you do get a very large display. It could be a viable choice if you're going to be permanently mounting it, but I like the Eigertek's size better. I've got one of the Amicos-- it is really small (about the size of a portable CD player), and is _very_ loud. It's not upgradeable though (soldered IC rather than a socket), and I don't think it's as well assembled as the Eigertek (nor can it be as readily repaired). It also uses a clunky Russian mil.-spec. connector for the power supply, so if you lose that you can't just run out to Radio Shack and get a replacement, and the power supply that comes with it is larger and heavier than the machine itself. I still like it, but can't recommend it over the better-made Eigertek.
If you've got a bigger budget and are going to be using the box extensively for tournaments, the the SG-12 remains a very good choice, and has a larger, more visible display and louder sound than the Eigertek.
-Dave