I disagree that there is no difference between the 72mhz systems and the Spektrum when it comes to low voltage. Here's the scenario:

Let's say your servos put a momentary load on the battery that drops the voltage below the critical voltage for the receiver. We'll assume that the voltage drop lasts for a very short time, 300ms or so. This is probably a real world scenario when entering a high g manouver. You will have a spike in load as you move several servos all at once, then the load will come back to "normal". Now with the 72mhz analog or PCM receivers you will have a 300ms interuption in signal/connectivity. You may not even notice the drop in connection. You only lose connectivity with the plane for the length of time the voltage is below the critical level. With the Spektum and I assume the other 2.4ghz receivers, when your RX voltage drops below the critical level,(even for just a couple milliseconds), you go into a re-boot and re-handshake with the TX. This can take seconds, not milli-seconds. Seconds of lost connectivity can be too much to recover from. I beleive these are the scenarios where planes are lost with "good" power systems. Quique had this happen at SEFF this year. I'm sure they thought the power system employed was adequate, and probably was pre-Spektrum. Check this article.

[link=http://www.horizonhobby.com/Articles/Article.aspx?ArticleID=1674]Horizon Article[/link]

BTW I've had my DX7 since December 2006 and put it in all my planes by Jan. I've had no issues with it and love it.