Additional $400? There's an 8GB on eBay right now, BIN, $425, only adds $200.
Regardless, you're still looking at a little less than half the 722, and the size isn't beatable for stealth. And how many festivals do folks really do during the season? I usually only do 1. We splurged and did 2 this year. ANd as mentioned, you're not spending the money on DAT or, god forbid, MD. Assuming this thing works as advertised, it's a great option for those that can't do the 722.
EDIT: Sorry, the 8GB isn't BIN, it's got bids....oops...