Mortarpod is pretty amazing with a flipped Garruk Relentless  ^{Flip  Flip}

do you find that you can really get by with only 20 land or do you have to mulligan pretty aggresively?

It's typically mull until you get a land and a mana dork, but with 4x of each, you don't have to mulligan too aggressively. Average mulligan for me over 10 games is 4 times.

I would prefer 4x es flying around, not to mention the hordes of fliers coming in Dark Ascension.

Also, I'm a sucker for Sword of War and Peace paired with Mirran Crusader (over Sword of Feast and Famine) for near-complete protection from colors.

I agree on Razorverge Thicket, I was thinking about using the scars lands on another deck for the same reason; the early WW. As for Ambush Viper, his lack of reach does limit his power considerably, so Insectile Aberrations could be a problem. I am going to playtest having both Ambush Viper and Beast Within, so that I can turn their flying creatures into 3/3 beasts to be killed by Ambush Viper. I like the utility of Sword of Feast and Famine more than the protection, since the boost from Sword of War and Peace is almost miniscule in the late game. I have not considered any DKA cards yet, so I will probably add a few tomorrow when I have more time to go through the DKA spoiler. Thank you very much for the suggestions Graft!

and when equipped to a Garruk, the Veil-Cursed deathtouch wolf, deals with Insectile Aberration too

I see the use, but I simply do not have room for it In this build.