I had considered removing case and making it longer, but I really wanted it to be shorter to avoid having it significantly increase the amount of data to write/type.  I already think it's too long, but I need to make sure it has some kind of sanity check, and enough entropy to be useful. 

On that note: at the moment, it's 7 bytes plus a 1-byte checksum displayed in base58.  That is 56 bits of entropy, drowned in 16MB of key-stretching.   56-bits doesn't sound like a lot, but the keystretching takes my i5-2500K about 0.25seconds to compute.  If you had just a single CPU working on that, it would take 580 million years to go through the possible keyspace.  Even with a multi-million-CPU botnet, you're out of luck.  And GPUs won't be very useful with the 16MB required per thread. 

I figured the case-sensitivity was okay, because I'm displaying it in such a huge font, it's obvious what is upper and lower case.   It can still be changed, though...