Well, I just read his comments, and I've owned a 1348 for about two months now, so I'll make a few of my own. Personally, I found the announcement of major increases in the price of the newsletter and an additional $100/yr for the online "bonus haps" more startling, but that's another story...
First, I absolutely agree that people who buy the 200-series mountaineer expecting to be able to use seriously heavy glass on it are fools. I never even considered this as an option. He is also right that the 200-series tripod isn't much lighter than its metal counterpart. Most of his comments aren't really negative comments about the 200-series Mountaineer, but rather about people using them as though they're a 410. He's right. It's not a 410. I'd use it for lighter gear when I want to keep total weight down, just as I currently do my 200-series metal Gitzo. I've never put my 600/4 on this tripod, and if I owned the 200-series Mountaineer I wouldn't, either.
As far as it breaking, he specifically mentions the top plate. I thought this was the same metal piece as used in the metal 200-series equivalent, but could be wrong. If I'm right, though, it's not a problem specific to the carbon fiber model, but rather this lightweight series in general.
In the case of the 1348, I've compared it side-by-side with a 340, and the metal top plate is identical as far as I can see, so any weakness here is shared with the 340 - Shaw's standard tripod.
As far as his comment that "only mass stops vibration", he's wrong. Carbon fiber is more effective at damping vibration than aluminum.
This is a fact. This is one reason why it's such a great material for tennis rackets, for instance. And it's always much easier to add mass to a tripod than to remove it, at least if you want the tripod to remain functional.
I'm surprised John considers a 340 adequate for a really long lens (he says it's his standard tripod). My 1348's lower leg section is relatively small diameter carbon fiber tubing - but so is the 340's lower leg section...
I felt a 340 was inadequate for a 600/4 in my fooling around down at Pro Photo here in town. A 410 is more than adequate. A 1348 seemed more sturdy than a 340 to me, though not quite as sturdy as a 410. The price difference was about $300 between a 1348 and a 410, which caused me to nearly buy a 410. I did get the 1348 because I do lug my tripod around a lot, including to my annual raptor migration project which is a backpacking situation. Not only do I lug stuff up there every year but I lug stuff all over the mountain for the few weeks I'm there. And I'm getting older...
Anyway, if I'd thought a 340 was adequate, I would've bought one. But I didn't feel it was, so the choice was between the 410 and 1348 from my point of view. I don't remember just how much lighter a 1348 is than a 410, but the difference is greater than difference between a 1348 and 340.
As far as the legs coming unglued, this is the first I've heard of it. I did have the opportunity to talk to some users before buying mine and none experienced this. Of course, none of them had been to Antartica. Durability was a question I had given the hybrid nature of the legs (i.e. the center plate and leg swivels are metal). If mine comes unglued, you'll hear about it just moments after Gitzo does. The Goshutes, the 9,000 ft Great Basin range where I band hawks, will present it with reasonably extreme conditions, from 100 degrees at the bottom to some nights in the teens, at least. Lots of UV, too. Humidity from bone-dry to dripping. Lots of lightning, another advantage of a non-metal tripod! The place wore out my tent after a few seasons, and dried out and cracked and otherwise trashed my rocking chair, we'll see what it does to my tripod.
John seems to imply that it's not hard to reglue the leg if it does come loose. That's some comfort.