I think the common argument against the Fostex R8s is the scarcity of parts, vs a relative of abundance of parts for Tascam machines The tascam machines aren't really that much more expensive than the Fostex R8, plus the Tascam decks are the larger format 1/2" 15IPS (with the exception of the 388).
I'll mention Otari as well, I just picked up an MX5050-8 for $350, which is a pretty good deal, and its a better machine than the consumer TEAC/Tascam machines. It took me a while to find this deal, so you may have to be patient.
just so you know what you are getting into... Be prepared, analog is an investment in time and money. I have been hunting down a deck for a good six months+ now. I have went through two of them, and I have probably spent more time tinkering, repairing, looking for parts, looking for a tech and learning how to maintain the deck than actually RECORDING with the deck. There are some great machines out there that can be had for pennies on the dollar of their original value, but even with the GOOD decks, there are hidden costs as well: replacement parts (yes, these old machines are gonna break down), test/calibration tapes, cabling, cost of balnk tape itself, etc... it adds up fast. plus, there are alot of lemons out there too, and its harder for a newbie to spot them.
cjacek's advice about buying locally is spot on. I would suggest craigslist in your home town, and it wouldn't hurt to put some craigslist wanted ads in some other cities nearby (within driving distance).
good luck!