I got this to work after doing a couple things. Not sure which in particular was the key.
As recommended by moonman here
viewtopic.php?t=5028&p=28109 ,I checked the filesystem with:
$this->bbcode_second_pass_code('', 'e2fsck -f /dev/sdd1 (where sdd1 is my new usb drive)')
Then, as recommended by sambul13 here
viewtopic.php?f=18&t=3355, I added a label to the usb drive, and added line to fstab for my boot usb disk (I also removed UUID mounts for usb drives that actually aren't present on my second pogo; and removed the swap mount I'd setup on the first pogo)
$this->bbcode_second_pass_code('', 'tune2fs -L urootfs /dev/sdd1')
fstab:
$this->bbcode_second_pass_code('', 'LABEL=urootfs / ext3 rw,noatime 0 1')
and it now boots.
Before doing this, I enabled netconsole and confirmed uboot was working, and kernel boot was actually starting. Kernel boot was cratering with:
$this->bbcode_second_pass_code('', '[ 29.135777] No filesystem could mount root, tried:
[ 29.140555] Unable to handle kernel paging request at virtual address 00303030
[ 29.148003] pgd = c0004000
[ 29.150745] [00303030] *pgd=00000000
[ 29.154367] Internal error: Oops: 5 [#1] PREEMPT
[ 29.159008] Modules linked in:
[ 29.162087] CPU: 0 Not tainted (3.1.10-15-ARCH #1)
[ 29.167255] PC is at mount_block_root+0x200/0x280
[ 29.171985] LR is at mount_block_root+0x1e0/0x280
[ 29.176713] pc : [<c052fbfc>] lr : [<c052fbdc>] psr: 40000013
[ 29.176718] sp : cf82bf80 ip : 00000000 fp : 00000000
[ 29.188255] r10: c049f440 r9 : 00000000 r8 : 00008000
[ 29.193507] r7 : c086195c r6 : c0551e7c r5 : cf812005 r4 : 00303030
[ 29.200073] r3 : cf82beb0 r2 : cf82bf74 r1 : c049f418 r0 : 00000039
[ 29.206639] Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
[ 29.213989] Control: 0005397f Table: 00004000 DAC: 00000017
[ 29.219760] Process swapper (pid: 1, stack limit = 0xcf82a270)
[ 29.225622] Stack: (0xcf82bf80 to 0xcf82c000)
[ 29.230005] bf80: 00000000 00000000 00006180 cf4a2980 00006000 c00d3508 cf8190a0 cf497300
[ 29.238226] bfa0: c049f440 00000001 c0593380 c0551e91 c000945c 00000013 00000000 00000000
[ 29.246450] bfc0: 00000000 c052ff3c fffffffe 00000002 00000000 c0558ee4 c0558ee4 c052f8c8
[ 29.262904] [<c052fbfc>] (mount_block_root+0x200/0x280) from [<c052ff3c>] (prepare_namespace+0x160/0x1c0)
[ 29.272525] [<c052ff3c>] (prepare_namespace+0x160/0x1c0) from [<c052f8c8>] (kernel_init+0x11c/0x14c)
[ 29.281717] [<c052f8c8>] (kernel_init+0x11c/0x14c) from [<c000945c>] (kernel_thread_exit+0x0/0x8)
[ 29.290644] Code: e1a00004 ebf3b517 e2800001 e0844000 (e5d43000)
[ 29.296930] ---[ end trace fad1f55e35d26a7a ]---
[ 29.301690] Kernel panic - not syncing: Attempted to kill init!
[ 29.307681] [<c000d290>] (unwind_backtrace+0x0/0xe0) from [<c03cc5d4>] (panic+0x58/0x198)
[ 29.315944] [<c03cc5d4>] (panic+0x58/0x198) from [<c0021a48>] (do_exit+0x88/0x7a0)
[ 29.323595] [<c0021a48>] (do_exit+0x88/0x7a0) from [<c000b8e0>] (die+0x1d4/0x200)
[ 29.230005] bf80: 00000000 00000000 00006180 cf4a2980 00006000 c00d3508 cf8190a0 cf497300
[ 29.238226] bfa0: c049f440 00000001 c0593380 c0551e91 c000945c 00000013 00000000 00000000
[ 29.246450] bfc0: 00000000 c052ff3c fffffffe 00000002 00000000 c0558ee4 c0558ee4 c052f8c8
[ 29.254672] bfe0: 00000000 00000000 00000000 00000000 c052f7ac c000945c fffffbfe fffdfeff
[ 29.262904] [<c052fbfc>] (mount_block_root+0x200/0x280) from [<c052ff3c>] (prepare_namespace+0x160/0x1c0)
[ 29.272525] [<c052ff3c>] (prepare_namespace+0x160/0x1c0) from [<c052f8c8>] (kernel_init+0x11c/0x14c)
[ 29.281717] [<c052f8c8>] (kernel_init+0x11c/0x14c) from [<c000945c>] (kernel_thread_exit+0x0/0x8)
[ 29.290644] Code: e1a00004 ebf3b517 e2800001 e0844000 (e5d43000)
[ 29.296930] ---[ end trace fad1f55e35d26a7a ]---
')