The UX team at the LDS church is second to none. They made a concerted effort several years ago to hire the best (within certain ecclesiastical constraints) and I think they've succeeded. I would hire any of them.
They have a strongly, user-driven dev process that brings high fidelity mock-ups into the process well before development starts. UX works directly with the customers (different organizations in the church) to make sure they get what that want, leaving the program managers to ensure delivery.
The underlying CMS (which I worked on), on the other hand, is something else. :)
Just yesterday they fixed one thing that bothered me about it, which is that anytime you highlight, you would get a fade-in pop-up on the side of the text about journaling or highlighting it. This was pretty irritating since I am in the habit of highlighting text while I read. Now there is a constant black bar that tells me to sign in to journal and/or highlight, which is also annoying, but less so.
Secondly, the new layout is not fluid horizontally -- it is horizontally centered and seems to be tailored for 1024x768 audiences. It's much worse attempting to read scriptures or articles on my 1920x1080 screen with gobs of excess space on the screen, now only occupied by blue gradient. The text used to flow well and take up all available screen space due to the simple layout of the site -- the revision not only horizontally centers everything, but even cuts the container down, with "Share" and "Download" links on the sidebar. The text is spaced awkwardly and it's just a great big waste of screen real estate. I read the print version most of the time (now I use the old one since they brought the old scriptures back), but it doesn't have footnote toggle and the spacing is still weird; at least, however, it doesn't waste 50% of my horizontal screen space. Loading footnotes can be tiresome, as the site makes an AJAX call on load; I'd much prefer preloaded footnotes. The new chapter selection page makes it harder to find the chapter you want -- you can either scroll a lot and use the same number of clicks or click on the jump menu and add an extra click in there.
Clearly the first one (ignoring for now that scrolling on Safari was jerky when I tried). The old one is fluid which is just a bad idea for long texts. Much more than about 100 characters per line reduce readability, using all the space on a 1920 pixel wide monitor is just a bad idea.
The new version could maybe have about one third wider lines but the seventy or so characters are a good number for texts on the web. The new version is beautifully typeset and has about the right line length.
Using all the available horizontal space on the web for text is nearly always wrong.
What's wrong with it? As I noted above, I clearly prefer it and have no problems with it. I've also never heard of anyone else finding articles or scriptures hard to read on the old site. It's not like the margins are set to zero, there's adequate spacing in everything I see on there.
On my 1440px wide screen one line has about 200 characters (maybe 30 words) if I maximize my browsers. It’s not so much a problem with the scriptures site because every sentence gets a new line and every line is numbered but there can still be sentences which go on for several lines. Your eye (and neck) has to travel all that distance and then go back and hunt for the right next line which is harder the further you traveled.
The guideline is to have about 100 or so characters on one line.
I guess it's just a matter of preference, though I can't imagine someone liking the wasted screen space. If a website doesn't use all my horizontal space, I zoom it up until the screen is filled. I find vasty backgrounds that take up 50%+ of the window distracting. I don't notice any additional neck or eye strain, and in fact notice less because it's much easier to read words.
I have to agree with you on this, nothing drives me more to distraction with modern web design than the tremendous amounts of wastes space on my screen. I do exactly what you do, zoom the page until the content fills the horizontal width of the screen. (Though often as not, I'm zooming in to the content to push sidebar adverts off the side of the screen like with this site http://www.geek.com/). I have a good solid 6-7" of wasted horizontal screen space ignoring the sidebar adverts, 3-4 if I add them.
All that being said, I do find that raw text that spans the screen to be harder to read...mostly because it's easier to get lost ending a line on the far right of my screen and returning to the far left (especially if the font it small, something that zooming the page up doesn't seem to have as much problem with).
I think the science on characters/line is sound. It would be really nice if they would add columns for wider screens though (or at least two columns like the print scriptures). Actually, the printed scripture is a good example of following the guideline to not have too many characters per line.