So this may sound like a bold statement, however when I look at this version of OSX objectively, I really do arrive at this conclusion. Bear in mind I have been using OSX since Jaguar and the only version I missed was Lion, so I do have quite a bit of experience with OSX. I haven't really visited this section of the forum since I wanted to get my own experience with the release over an extended period of time. I think its safe to say that I've had enough usage now to share my thoughts. I will try to explain each criticism in a concise manner, and refrain from letting my personal feelings hinder objectivity. Let me start by saying I have been using Mavericks mainly on two Macs, listed below: - 2009 15.4" MacBook Pro, 2.66GHz C2D with 8GB RAM - 2010 27" iMac, 2.8Ghz i5 with 8GB RAM While these machines aren't using the newest chipsets, I've never had any problem with them before regarding performance. In fact, I think I saw a beach ball briefly maybe once a month on my 2009 MBP with the previous releases, now however is a different story. I've never had significant performance issues with either machine, so I simply won't accept any excuses like "your machine is too old". 1. The most sluggish start up ever The one thing which made OSX so superb in my opinion was the lightening fast start ups, once the machine was turned on, you were good to go. You could do anything, immediately. Now, the total opposite is true. When the OS is loaded, it is immensely slow for several minutes until the bowels catch up with the visuals. Upon start up, once the dock is loaded, if one clicks an application, it will happily bounce there for what seems like an eternity. Almost nothing responds instantaneously anymore. When clicking an application, it will bounce and bounce and bounce. Right click the app to quit.... the dock will freeze for a couple of seconds and you will have to force close or just wait for the bouncing to stop. Open up multiple apps.. well you might as well go and make a coffee while you wait. This is perhaps the most irritating thing about the update; the general sluggishness on start up. I should mention that I am not only talking about a boot up from shut down, these problems occur when awaking from sleep. Very rarely, this will not occur or it will be short lived, it literally occurs every time. 2. The seaside? Quite literally.. Ok.. I get that they were inspired by the seaside and surfing, but I think they took this far too literally, because all I see with this release is beach balls. I see so many of them, one would think it's a deliberate visual reference to the beach! It really is abysmal. As I said before, on my MBP or iMac, I literally saw a beach ball maybe once a month and that was for good reason, say if I was launching a tonne of apps at once. Now however, I see beach balls everywhere! And every single day! I click on the reminders app, I am greeted with beach balls and bouncing. If I try to switch quickly between multiple apps using fairly minimal CPU power, again there are beach balls. I try to drag a large file into iTunes, well you can guess what happens. I could cite hundreds of examples on this issue, but I think people will know what I'm talking about. 3. Power management? So this one is tricky. As I said, I am using a 2009 MBP to judge the power management, so the battery life isn't going to be as great as a new MBP. However, I think its safe to say that the battery performance should not be worse than before. Although my battery is 4.5 years old, it still contains around 75% capacity through deliberate care and maintenance on my part. I have maintained and cycled the battery pretty well to maximise its life. Previously, I was getting around 4 hours of battery life on Mountain Lion, from 100% down to about 15%. This was using WiFi with several applications running in the background but nothing that was too taxing on the CPU. On Mavericks, I get around 2.5 hours of usage before my battery is dead. This is quite a significant drop, and occurs when using the same applications. The battery life has definitely seen a drop, no doubt about that. Not only that, the power management seems far less secure than it was before. Previously, my Mac would still be usable at 3% battery life. On Mavericks, the computer will literally shut down when it gets below 30%! This really is a huge issue, and I'd love to know if other people are experiencing this. It almost feels like once I get below 30%, the computer can literally just shut down at any time. Yesterday, it just went dead on me at 22%. I was working, and it just went black, no warning or notification. I'm very disappointed in this, since they advertised "Power Management" as one of the new breakthroughs, and I was expecting this to breathe new life into an ageing battery, in fact it has made performance worse. If anyone with a new battery could comment, it would be interesting to hear about your experience on this. 4. Airdrop is very selective Airdrop in my opinion has never been entirely stable, I've always had issues when sharing with other Macs. On ML, it would work most of the time but sometimes it would not initiate the transfer and get stuck on "waiting to accept". On Mavericks, the same issue occurs but more often. I have never been able to share a file with another 13" 2011 MBP in my house, but for some reason it can share with another 15" MBP in my house. What's this all about? Why can it share with some computers, some of time time, but not with others? It just seems buggy and it still does not work as it should. 5. The ever-changing wallpaper I know of others who have experienced this issue so it is definitely not isolated to my experience. Sometimes, the OS will take it upon itself to revert the wallpaper back to the default surfing one. This can happen when opening a new desktop in Mission Control, or when booting up. Not a big issue, but it should not be happening. 6. Icons getting stuck in the dock This one is a little strange since I have never experienced it before. When one downloads a file, it goes into the downloads folder. I personally have this located on the dock for quick access. Sometimes, the icon will get stuck though. The status bar of the download will not disappear from the icon so one has to remove it and re-add it into the dock. It isn't major, but an annoyance nonetheless. These are the main six points that I can think of right now, and the first three are pretty huge. There are other issues, however I have discussed quite a bit already and I don't want to bore anyone so I shall leave it at that for now. Overall I would say this is a very disappointing release, not because it is unusable, as it certainly isn't. It is still a usable, however it does not reach the bar of stability that the other releases achieved. It feels rushed, buggy and unpolished. Any thoughts or comments on these points would be interesting to hear.