This topic was discussed here:
http://www.3drcforums.com/showthread.php?1325-IBEF-versus-Opto-Kill&highlight=ibec
[MENTION=109]NJSwede[/MENTION] did a nice write-up describing the differences between and IBEF, Opto Kill, and IBEC. An Opto Kill only provides perfect signal isolation only when using a separate pack for ignition. The fiber optic is only a switch that gets its signal from the rx. It does NOT transmit power to the ignition.
So... if you power your ignition with the same battery as the rx you are running a risk of ignition noise coming back through the power connection to the battery and into the rx.
If you think I had fun putting my plane into the ground twice within a few weekends due to this issue you are sadly mistaken. I am glad some people have success with this but I am telling you it is a ticking time bomb.
I just brought this up to point out a possible setup flaw that could cost a plane.
I am not trying to be an alarmist and I will concede that perhaps not every opto kill has the same design specs.
I don't buy into the argument that a battery is a good RF buffer. I also think servos are not all going to react the same way to the RF noise from the ignition.
I also want to point out that I ran this same setup on a 70" slick for many many flights without an issue... then I had a plane into the dirt twice within a couple weekends. I am running the same setup now with the only difference being an IBEC instead of an opto-kill on my single LiFe pack setup. I have had no subsequent issues with this gear.
FYI the servos that freaked out are power HD 1214TG (I think that is right off the top of my head). They have been great "budget" servos but are slowly being cycled out for savox. I still have a pair of them on ailerons.