I haven't competed in a long time and when I did it was all local smokers, but I'm in much better shape now.
I've done BB twice, the first time was after reading Joel Jamieson's book. But I didn't really adhere to the principles or set things up properly. I didn't do it for very long and wasn't strict with HR or session frequency + duration. Basically my first attempt at Base was just adding in a few long runs, so I didn't notice much.
2nd time around I decided to take it a little more seriously and ran the template from TB2. That was a lot easier to follow because everything was laid out "do this" style (session frequency/duration/HR zone etc) and it was easy enough to understand that I could sub in other sessions from the Vault if I wanted to change things up a little. I also tested a bunch of benchmarks before and after; 5k, 1.5mile times, max push-ups, pull-ups etc. so I was clearly able to see improvement or lack of improvement (lots of improvement). My results are still in my log somewhere.
As far as the anaerobic/aerobic thing, if you read TB2 and Joel Jamieson's book you'll see that fighting and other activities commonly thought of as primarily anaerobic really aren't -- and rely a great deal on the aerobic system. The aerobic system resets or recharges the anaerobic system so the better your aerobic system, the more efficient and powerful your anaerobic system's going to be.
I train mostly to support my Muay Thai, and after Base it was night and day difference in the ring (sparring). I have lots more in the gas tank, and my reputation during sparring changed from being that strong guy with no gas to being that strong guy that just keeps going. Another thing I notice is that all my HIC workouts have improved post-Base. In one instance I was able to double my # of rounds. And HICs are pretty much all anaerobic or work capacity.
Keep in mind I've never trained the aerobic system/muscular endurance in isolation before Base, so maybe if you already have a good aerobic system you don't need to do it. Like if you've trained for marathons or Spartan Beasts or something before.
