The "fight energy" that is mentioned is the mindset necessary for actual street combat (and is very applicable to sport combat as well).
Basically, if you look at a lot of circuits and conditioning routines they are time/reps oriented. Meaning, they are in 4 round intervals, or so many times through the circuit, etc...
The CRAWL, just like combat is goal oriented. In other words, you learn to keep going until you finish the task at hand, not just continue until 4 minutes has gone by. It develops a "never say die" attitude.
I would say it differs from traditional circuit training in that:
1) there are some unique exercises
2) it builds tremendous grip strength and endurance (something that a lot of traditional circuits do not adequately address)
Things like crossfit are good and I know some MA's who use it and like it. I know one guy who loves it and does it all the time, his conditioning while doing calisthenics is phenomenal.
But, he'll openly admit that crossfit isn't even close to Lysak's conditioning routines when it comes to carry over to combat. The guys who I know who have done the CRAWL for an extended period of time and progressed on it like you're supposed to are absolute animals.
As far as energy systems, stuff like that is honestly over rated in my opinion. What matters is results. Sure, there is some truth to things like that. But seriously, let's just say that it'll allow you to go balls to the wall for what seems like basically as long as you want. You'll pretty much be able to keep the intensity extremely high for extended periods of time, thus allowing you to out last those with similar strength levels, and steam roll through those with lesser strength/conditioning levels.
Just look at guys like Sherk. Sure, he doesn't actually do the CRAWL, but his training is based around similar methods and a similar mindset. Wrestlers in general tend to have a dominant mindset where they just push the pace and often times win by attrition. The CRAWL will develop that level of strength endurance and conditioning.
On top of all that, the program is progressive. So, as you get stronger, it continues to get harder, thus making it theoretically infinite in it's strength and conditioning capabilities.
But seriously, if you doubt it's effectiveness, buy the dvd and try the routine. Once you do it once you'll realize just how ridiculously intense it is. And if you stick with it for a few months, you'll see results on the mat.
As Lysak told me (and several others that I know who he has given the routine to) "I'm not going to tell you the results that this routine is going to give you. If you do it right and stick with it, other people are going to tell you the results. You'll have people coming up to you after rolling saying things like "Holy crap! What the hell have you been doing?"."
If you have any further questions feel free to PM me.