I guess I’m in the minority here… I rather like it. Crisp and clean… and it seems snappier than mavericks on my computer.
I have a newer macbook with the retina display. I’ve heard it looks rather funky/blurry on a non-retina display.
I like it too.
The transparency is a bit much, but I can get used to it (or turn it off).
I’m in the like it camp. I even like the transparency.
Overall, a very attractive UI.
This would not be helpful for any of the elderfolk in my life. When short term memory goes, there is just no learning new things and any deviation from what has become habit is a real problem. The absolute worst, IME, is not minor changes in interface, though, but password management. 
OK, stupid question. What is the transparency thing? I haven’t really noticed it, but maybe it’s because I have a plain gray screen as my background?
Yes. The menus and dock are mildly translucent (although much less than, say, the task bar in Windows), and some utility windows (the display part of the calculator widget, for example) are also slightly translucent. If your background is uniform, you probably wouldn’t notice it except if you overlap a widget window over something else.
Here’s what made me LOL:
Scroll the SDMB page up in Safari, and watch the title bar/favorites bar…
The banner header for this site made the tabs turn different shades of blue and then my Fav bar was another shade and the URL window was yet another shade of blue. And then it sort of changed as I scrolled down the page… it was really annoying but now that I turned it off, it doesn’t annoy me at all.
ETA: Yeah, see how freaky it is, beowulff? Bleaaaah feature; go away.
Ah. That is a weird aesthetic decision. I use Chrome, which is why I haven’t noticed it.
Nah, it looks fine on my 2008 iMac. Though I may need to download the tool somebody else mentioned to return the default UI font to Lucida Grande. I like the new font, but for some reason it’s hard to read for my aging eyes.
I’m liking it too. I’m not a customer for the latest hot new features - I do what I do with my Mac, and I’ve upgraded steadily with every iteration since System 7.6.1 to Yosemite. New features are integrated into my habits if they’re useful to me, ignored if they’re not. Like … Spotlight (along with Windows’ hot new search features). I never got all of the hype over Spotlight. I know where I put my crap, and have almost never needed to use Spotlight. But it was revealed to me a few years ago that, yes, there are people who save files without having any idea where they went.
While part of me would love to be able to totally customize my GUI (as mentioned above, I was an active and prolific member of the Kaleidoscope community back in the day), over the years, I’ve realized that one of the best things about the Mac OS GUI is the fact that it stays the hell out of my way. I’ll go ahead and equate the GUI’s job with the job of an umpire in a baseball game. As the saying goes, “You know the umpire is doing his job well when you don’t notice him.” And yeah, that’s the job of the UI. Make things work, but stay out of the way.
Hmm. I’m using Safari, and I can’t tell what we’re talking about. There’s no transparency in the Safari window at all, that I can see (and I don’t have it turned off, unless there’s a setting specifically for Safari somewhere). If it’s there for me, it’s literally invisibly subtle, even over a B&W background.
ETA: Oh, wait. I see it now when the banner goes behind the title/favorites. That’s what we’re worked up over?
It’s a very blurred and frosted, but nicely saturated effect. I like the aesthetic, personally. It adds color and variety subtly to an otherwise colorless UI.
It’s the same sort of effect that’s been going on in iOS.
Well, to me all the flashy stuff gets in the way. I’m not saying it has to look like the UI from 1984, but I wouldn’t be totally against it either. I don’t use an OS to look at the OS, I use it to actually do things.
That’s what I said 
Aye, you can. But it turns out they switched out the noise from POINK to “rapping on a glass bottle with a mallet”. It’s even more annoying than before.
And yeah, I tried to change it, but that noise seems to be the default and only selection.
I seem to have found a bug in the new Safari. If I click on a SDMB link in a reply notification e-mail, and then continue reading the following posts, at some point after scrolling down Safari will abruptly, by itself, scroll back up to where I started.
There’s one good thing about Yosemite; XCode support for Swift pretty much came with it.
It’s not that they can’t, it’s that they choose not to.
My guess is it’s a combination of the things other people mentioned. Themes increase the support burden. Themes aren’t a feature enough people care about. Themes increase the development and testing time of everything, since you have to make sure that things look good with all sorts of different varieties of theme options.
Lazy is a poorly chosen adjective. It’s not like the companies are just sitting around loafing. Clearly they’re working on other things that are not themes.