I've been able to put in more time with the Amp Grinder, and here are my observations:
-It does indeed have Loud of God
-The calilil demo is dead-on, it sounds EXACTLY like those examples. The only thing I think it doesn't quite capture is just how beefy it can be
-It passes the Ace of Spades test and the Lateralus test with flying colors. It loves doomy riffs, and sounds great with power chords
-It sounds really good with all of my basses (p-bass, L2K in all modes [incl. inner and outer coils), and even my fretless jass with ground wounds. This is notable because my previous arrangement with the crossover sounded great with my p-bass, but never sounded right on anything else.
-Even at higher gain, the personality of the instrument still came through and was differentiated between basses
-It stacks well with OD or boost in front of it
-The way the clean blend works, the slow menacing sweeps from the Microsynth earlier in the chain still come through
-The volume level is unchanged when switching between modes I & II
-It's not finicky, it's really intuitive to dial in
-It's the lowest-noise Rat I've ever used, by a significant margin
So, needless to say it's a keeper, Velcro went on it last night.
Very persuasive.