These apps are often in the corner of the screen while working with different applications; they should be minimal and not full of harsh textures and deep bevels. Also, they're just plain ugly.
Here's a screenshot for those not familiar: http://f.cl.ly/items/3R0I3X2Y041b091l0j1w/Screen%20Shot%2020...
No one in software at Apple seems to have the vision required to make positive changes, rather than cribbing from iOS as the Lions have. Jonny Ive can keep hardware running well, but software is languishing.
It used to be such an easy choice as to what OS I wanted. Mac OS X was prettier, more stable, more fluid and had better apps. I think Windows 8 is a much prettier OS, although the apps aren't there yet. Ubuntu is also plenty usable, has the UNIX underpinnings, and is less ugly in a number of spots than OS X (god I hate linen, and I have no love for skuemorphism). I've strongly considered running Windows 8 as my host system and virtualizing Mountain Lion, although I'm leaning towards sticking to Mac as host for now.
EDIT: FWIW, I would note that Apple's core programming: system libraries and such, remains top notch. It's the front-end that seems fairly clueless.
Now, Lion seems to have slowed down my 2010 Macbook Air- at times it absolutely crawls when I'm positive it never used to. Is there anyone out there running Ubuntu full time who can say how good driver support is? In particular the trackpad- I've never had a perfect trackpad experience outside of OS X, Windows hasn't been able to do it either.
Because there's no setting for automounting and unmounting a Time Machine drive, I ended up using my old Macbook Pro as a file server and plugging in the external to that, then using a hack to get Time Machine to recognize it as a Time Capsule.
sigh
That's not Lion (same system, OS, identical performance to day 1). I'd fire up Activity Monitor and see what's active when it's slow - there's probably something causing a ton of background I/O.
There's a limit, of course. I saw a screenshot of Mountain Lion where Reminders was a yellow legal pad with scratchy red coloring-pencil markouts on finished reminders. That was harsh.
But I find even the ugly examples are almost always superior to the days of uniform chrome like the Win2000 era: http://cdn.ttgtmedia.com/digitalguide/images/Misc/da_screen.... -- where you could squint your eyes and become unable to tell apart the programs on screen.
The leather is mildly ugly if I focus on it (never), but Google Calendar's harsh asymmetry, nonsensical color scheme (cartoonishly highlighting two buttons - "SEARCH" and "CREATE" - I never use), and inability to hide numerous unused elements bother me every second I have the tab open.
I don't understand the value of these discussions about design that start and end with how skeutomorphic an application is. It's one of dozens of design elements, and it's disappointingly rare to find a well reasoned argument (not "I dunno, Windows 8 just feels cooler now") why skeutomorphism is categorically bad design.
I'm not trying to point to an Apple/Google horserace, but seriously, there are other aspects to design then skeutomorphicness. Textures that appear as subtle gradients in your periphary are barely noticeable for most the vast majority of the population. I mean, just ask a non-geek iOS user what they think of the silk texture in iOS and prepare for a blank stare.
The steam engine's fine, everyone needs to stop over analyzing.
WE don't like the skeuomorphic stuff (no need for quotes, it's a real word) but the general public does. It demos well and makes software more approachable.
It drives me nuts, but I'll bet it's here to stay. At least until the first video game generations are retirees.
Source? We don't have much data to measure the fondness of end users for skeuomorphic interfaces of the Mac OS sort.
You mentionned some of the reasons to make UIs like that, and of course Apple is selling trunks of devices, but how do we know that users specifically like Calendars, Reminders, the Fullscreen mode of Photobooth, etc. ?
As a more serious attempt to back that opinion up I'd say look at the success of Apple's design in the marketplace over the last 10 years - pinning that exclusively on their love of skeuomorphism would be iffy, though.
Maybe that's the rationale behind it in the first place? "It's so cluttered... Let's make these apps' looks really distinct so they really stand out..."