For what it's worth, I bought a RT700 which was delivered last week. That thing is definitely stout, very heavy and seems well constructed.
When I was unpacking it, I noticed the porcelain coating was missing in a few places, like it had rubbed off by hitting high-spots on the barrel during transit. I wouldn't have normally even bothered about it but it had left some rust on the nearby stainless and I live in a very humid environment so I figured i'd get ahead of it. I called Rec Tec just to let them know (so I wasn't calling 3 years later with a "It was always like this!" call) and expected to get some touch up paint. Without hesitation, they offered to ship me a brand new lid. That's impressive CS!
One thing I did notice, however, which disappointed me a bit - the stainless on the barrel and exterior is 430, not 304. I found this out accidentally because my Smoke fell off its stand and stuck to the side shelf, which I thought was going to be non-magnetic. that prompted me to test a few other places. Basically, the bull horns, the pull handle, grates, drip pan and deflector are 304. The rest (side shelf, barrel, smokestack lid) are 430. I don't need to have 304 just so I can brag about the quality of my stainless, but I do hope that the 430 holds up well.
I called RecTec about it and they said not to worry about it, that barrels and side shelves never go bad, it's the internals that matter. Of course they're biased on that front, so we'll have to see. I only mention it as I thought the stainless steel barrel was going to guarantee longevity when I ordered it and I'm now wondering a little bit. I'm sure it'll probably be fine though.
Interestingly enough, according to the product description page, the 680's side shelf and smokestack lid are 304 stainless. I asked Rec Tec if they changed it recently and they said they weren't aware of a change and that they didn't think they'd ever used 304 for the side shelves.