I just beat Bardel yesterday. Game time was 4 hours, 4 minutes (I'm the determined type, but no it was not all in one sitting).
I wasn't nearly as clever as Use Terps, as I didn't manage to get to the first emitter in time to defeat it. Although ironically my strategy was far more Terp-heavy than yours (sorry I don't have screencaps with me). I started on the middle spire, placed a few collectors and built a wall guarded by a single mortar. Then I spanned to the spire to the right with relays and did the same. I'd now consumed two of my three allowed mortars, but was free to use my energy to get to the spire to the left with the AC emitter on it, which was flooded by this point. I built a third wall with the third mortar guarding it. At this point I had enough real estate to get 4.6 energy from the collectors. I then went after the left-most emitter, drained the creeper lake to the northwest and took the northern island.
I recommend what you said about turning off your beam towers whenever the AC spores were launched. It got to be incredibly frustrating turning them on and off once per minute for the first few hours it took me to finally take out the spore launchers (save often - forgetting to turn them back on just one time will ruin your day). But worth it, because I took that strategy a step further. I built a handful of Sprayers and set them to collection mode. After a while I'd built up a small army of fully loaded Sprayers even though there isn't a single mine on this level. That came in handy because by the time I went on the offensive, the creeper was really deep. I built a level 10 platform for each nullifier, and as you mentioned, recycling PZ's for super-nullifiers helped gain momentum, as did placing the precious few collectors on them. I wish I would have thought to put my beam on one. I was mostly using them for mortars. Through most of the game my energy was running a deficit of 6-8, which was alright because mortars don't need to be firing at their full rate to hold a wall anyways. However to make my offensive push I needed to SLOWLY build up an arsenal of guppies to keep the blasters firing long enough for the nullifier to finish.
Cavemaniac, what happens when you snipe a runner on the northern island? Did I miss something?