After testing Yosemite for over 2 months, here's what's DOA about it so far...
I tested Yosemite, from the day it got announced, on a corporate environment, on a non production macbook air. I had a million problems, but that is what a DP is...
#1 First off and this is embarrassing for Apple, but the Feedback program while collecting data from your computer disables your ethernet internet! I've complained since day 1. They never fixed it. Reported since BETA 1.
Are you a developer or a public beta tester... ? I used the apple bug feedback tool for developers and it worked as it should... Did you install this on a production laptop or a test machine?
#2 Plugging in any iPhone, at least since IOS 8 (or the latest 8), disables your bluetooth completely, meaning goodbye Magic Mouse, goodbye wireless keyboard. Seems to only happen when the iPhone is completely charged. But only solution is a re-boot or standby peripherals. COMPLETELY UNACCEPTABLE.
This must be you. I have been using the trackpad, the magic mouse, and my logitech H800 Bluetooth headphones without any issues.
#3 No clue as to whether this is related to #2, but constant warnings that Apple iPhone peripheral is not compatible with this phone. Doesn't matter if it's Apple's cable or not. iPhone is then not recognized and Image Capture program fails to work and charging stops. Tested with several iPhones, same result.
You are failing to mention which build have you been using and what iOS version you had on the iPhones..
#3 No sound on SOUND keys as in you can't tell how loud you're increasing the volume from the keys. Also sound to send mail is so quiet, you'll never know if you sent the mail or not. Reported since BETA 1.
This is not a bug. It's by design.
#4 Displays issues. No matter how many times you change it, Displays will not boot to the correct display you've set. For people with multiple displays, this means turning on another display or in my case having to switch to an HDTV to boot up and log in. COMPLETELY UNACCEPTABLE! And I've reported this since BETA 1 too.
Don't know what to tell you. My test laptop is connected to a cheap-o dell monitor using thunderbolt to dvi plug and a native thunderbolt LED display and I have not experienced this issue. Again you are not saying which build you are using...
#5 Some Mac OSX partitions are no longer compatible with disk repair software, so be careful. You'll get a warning that your disk mapping on a drive is no longer compatible.

I have never experienced this either. I have tested on a MBA with 256 FlashDrive and Macbook Pro 13" with a 500G HDD (non SSD) and a MBP 13" with a Corsair SSD, and this was a non issue.
#6 There is no indication as to when Spotlight is indexing. That's very annoying since normally you'd wait until indexing stops to use a Mac because of the slowdown.
Spotlight in Yosemite indexes when your system is idle and not doing anything cpu intensive.
#7 Preview loads for no apparent reason when an iPhone is connected. No clue why.
Never have experienced this... either. Don't know what to tell you.
Yosemite is NOT READY FOR PRIMETIME in my opinion after 2 months of frustration. I feel like Apple owes me money. Oh, I should add, the installation corrupted my Mavericks installation too causing all Mail accounts there to be corrupted, but I can't say that's related to Yosemite except that it doesn't like other Mac OS X partitions. None of the above problems happened in Mavericks.
I think that you were a casual user, who got excited at all the pretty stuff Yosemite had, and you decided to either download a Developer Preview from *cough* torrent site *cough* or you are a legit Public Beta tester... Either way your review is very amateur-ish. You never present which version of the DP or the Public Beta you are using. Did you use a testing macbook pro or iMac or mac pro? or did you installed this on your production computer?
There is a reason why Apple and many other developers releases these previews or beta's, and its for this same reason, for people like you and me to test their software. Report when you find something that doesn't work or test on your current enterprise environment.
In my experience, and my testing in the Enterprise, Yosemite DP1 was a shell.. basically I couldn't join the Domain nor run Lync or connect to exchange. It was pretty and that was about it... This went on for about 2 or 3 Developer Preview builds more... It wasn't until DP5 that I could do any of those things above, and trust me, that is the meat and bones of my corporate structure...
Even when we passed it to other Tech Support Groups for further testing, we advised them not to use any of the builds we were sending on a production computer...
I really don't know what to tell you other than... wipe your computer clean and make a clean install of the OS. For me, (and I have been running it for 2 weeks on my production iMac), it has been pretty solid so far. I can connect to exchange and Lync finally works super well. I have been able to test a few of the gimmicky stuff like Continuity and hands-off...
One of the few things I have not been able to test at all is receiving iPhone calls on my computer. I have not been able to text people that are on other phones other than iPhones from my mac either.
Every testing experience is different, people need to remember that it is a Public Test for a reason... These tests are not only for your amusement but for you to see where they fail so you can let the developers know where they need to pay attention.
Whining and crying during a beta is kind of Meh. The only thing I can do for you in that instance is offer you a hankie.