I bought the 680 when it first came out
after 3 months the main board crapped out and I sent it in to the vendor for repair
after 2 months and no word I contacted the vendor, and they dealt with TEAC
TEAC did replace that faulty unit with a new one after waiting 2 months
I know another member on this board (Chuck) who had the same problem
and now it appears as though tgakidis is having problems with one of his channels
that is all I have to say on the matter
I cannot speak about the R44 since I have never owned one
I can't speak about the DR680 as I've never used one. But, I have heard some great tapes made with them.
That said, I
can chime in on the R-44's reliability as I was one of the first kids on my block to have one; a stock model since late 2008. Since then it's been accidentally dropped, kicked, and has taken a few small liquid spills. Never had an issue with any of the electronics, inputs or outputs, never an issue with an SD card, it's never lost any of the many recordings I've made with it and, aside from burning through improperly charged rechargeable batteries (my fault), I've never had a lick of trouble with it. Works every time as it's supposed to work and I still pull great tapes with it. Wish I could say that about every piece of gear I've used. They'll take my R-44 when they pry it from my cold, dead fingers, etc, etc...