Like I said, not too big of a deal for me. I'm running linux on my laptop. It's nothing to format into ext3 and read it.
I'm gonna test this and see if there's any major changes. Will update.
Update #1:
Card will update to ext4, however andriod doesn't like the format. Go figure :3
Trying to do ext3, but the card doesn't want to format into it. It will go to FAT the ext4, but every time I try 3 the card stalls.
Update #2:
Found the issue, don't try to format through the phone. Use a reader

Anyways, I flashed a spare 2GB card with ext3 and I got the same story as ext4, android doesn't want to mount the card due to a "blank or unsupported file system" and unfortunately, same story for ext2. I'm gonna try less conventional formats to see what exactly android will accept in forms of sdcard formats.
Update #3:
Pointless. Android is too picky on what it wants in that slot. It will NOT accept any format except FAT (including ntfs). So then I thought I'd try to be sly and set the sd card's partition flag to say it was a FAT even though it was formatted in ext3. Nope. Saw right through it. Whatever it is, Android looks beyond flags and looks at the actual format it's self when it does it's little media scan. And just to see performance wise if flags did make any difference, I formatted the card into FAT and set it's flag as Linux. I actually got worse speeds than the card's stock format. It's not by much, but still about a whole mbps. I'm gonna play around with flags a little more to see if I can get anything better than the stats I posted below, but I doubt it. This is completely busted unless a future build can maybe find a file in the system that controls what the SD reader likes.
Test file: 100mb in 64 files
Stock
Avg Read: 10.1 mbps
Peak: 10.4 mbps
Low: 9.4 mbps
FAT w/ Linux flag
Avg Read: 9.3 mbps
Peak: 9.8 mbps
Low: 6.4 mbps