Like WordPress states on their WordPress 3.2 pre-release page client’s hosts need to be using MySQL 5 and at least PHP 5.2.4. There’s a plugin called Health Check that will let you know either way. I’d hurry and install this plugin because if the environment is not OK you’re going to have to login to the client’s cpanel and see if you can upgrade both or if you have to contact their host and ask them to make this an option.
The other big change is that WP 3.2 uses jQuery 1.6.1. You may be using jQuery plugins or random JavaScript functions that will not work with 1.6.1. I beat my brains out for a while before I realized that something I had written or included was the reason my custom slideshow wasn’t loading. I knew it was a Javascript error because an alert popped up instead of the slideshow and all it said was undefined. So now I have to track down what is not compatible or undefined. Yay! But I needed the site to work right now so I replaced WP’s jQuery 1.6.1 with jQuery 1.4.4 to buy some time until I can find out what is not right with my scripts. But I’m not betting much on fixing the scripts and will probably just phase out using them in new projects… too bad because some of them worked really well.
Oh I forgot to say whether replacing WordPress jQuery 1.6.1 with jQuery 1.4.4 causes anything to break. I’ve tested the Widgets and Menus manager and everything works as expected.