Should you update to WordPress 3.5
Of course you should! The question isn’t whether or not you should update your wordpress site, it’s when should you update your wordpress site! With any huge release, there’s a period of time you should wait to let other plugins and even wordpress itself fix a few bugs that are bound to arise with such a release.
Personally, I don’t update my sites or advise clients to update their wordpress sites until the next release, OR until at least 1-2 months have gone by since the release and plugins are ready to be updated as well. One, it will assure that plugin updates will be compatible with the new WordPress, and WordPress will have enough trouble tickets to know what needs to be fixed and will most likely have another upgrade available (aka WordPress 3.5.1 or the alike).
So cool your jets if you have a site that can’t afford any downtime or you don’t have the funds to hire a website designer to make sure the upgrade was successful and there are no glitches with your plugins. Upgrades don’t go anywhere, so just be patient until you can be 100% confident that it will be a safe transition.