This is the first year that I've been officially part of the Apple Development Community, and as such the first time I've ever used a pre-release version of an Apple OS.
I loaded Mavericks onto my old MacBook Pro (mid 2007) when it was released as version 6, a couple of months ago. I was genuinely pleased that it loaded and ran on a relatively old machine. To be honest, I really don't use the MBP much these days, so it was a fairly safe bet, but because I don't use it that much, I wasn't really getting a good handle on of the Mavericks experience. But two things were for certain - the machine wasn't crashing and performance wasn't being stifled.
So I decided to repeat the exercise with my 2011 MacBook Air. By this time we were on version 8. Once again I had no problems with the installation or general performance. In fact, in many ways I couldn't really distinguish much difference over 10.8 Mountain Lion. With one major exception. Safari turned into a disaster zone and became virtually unusable. I'm not sure what caused the problems, and I wasn't going to hang around to find out. I restored Mountain Lion (luckily without any incident) and reconsidered the warnings about not using beta versions of an OS on a workhorse machine.
With the release of the GM version of Mavericks, I decided it was worth another go. The experience has been much less painful - but I do still have some quibbles with Safari, almost all of which are around the problem of not being able to click on links. Some of this is down to badly designed websites which are clearly only designed for IE, and maybe Firefox, but it still causes me some pain.
Some of my newly discovered toys don't work anymore but I'm not too surprised at that, as they almost all do some shenanigans with the core UI code. But some of them, such as Flavours, already have beta versions that will, and do, work under Mavericks. 1Password 4 is causing me some teething troubles - it installed OK but is prone to tantrums (it's having different tantrums under 10.8.5 so maybe Mavericks isn't the problem here). I find that occasionally some applications don't seem to want to load, no matter how many times I try. Terminal and Contacts are specific examples. But a reboot does seem to fix that - I'm thinking this issue maybe due to other beta software
I'm guessing that between now and some time in the next few weeks, before the offical public release, we'll be seeing a flurry of activity from developers and new releases of software will be a regular occurrence. And then the auto update feature in the Mac App Store will be a real blessing as it already has proved to be under iOS7.
Batttery life does seem to have improved considerably, so there is clearly a lot of stuff going on under the hood. My third party battery status software is showing that I've got 85% left on this charge and it's estimating that it's good for 5 more hours. Admittedly that's with most background apps switched off, but it's still much more than I'm used to.
For now, I'm happy to keep the GM release running on the MBA (although I think I'll keep the iMac on Moutain Lion). Which means I can start using some of the other features I've been reluctant to try, especially File Tagging. And if 1Password continues to misbehave I may even resort to KeyChain in the Cloud. We'll see. For me at least, there is every reason to take advantage of the full update when it is made available, especially at the price point widely expected to be around £20. Even if it is a whopping 5+ Gb of download!