I'm not sure if this is actually an issue or whether the functionality has just been changed slightly. Apologies in advance, if the latter.
When inserting images into your page you can no longer simply click multiple images to select them. You need hold down CMD/CTRL to select multiple images. In RC2, if you wanted to insert multiple images at once (not a gallery), you could simply click on each image to select them and then click 'insert into post'.
(just to clarify, this is not inserting a galllery. That works fine. This is just when you want to 'insert into post')
Tested in FF 16.0.2 & Chrome 23.0.1271.95 on RC3