The window buttons weren't just moved from the right to left corners in the Ubuntu 10.04 beta, they were rearranged in order. Being a Linux system though, you can fix what you don't like with a few tweaks.
At the How-To Geek's home away from Lifehacker, Trevor points out something we'd known of before: the gconf-editor tool can rearrange the window buttons in a GNOME desktop (and hide desktop icons and change a few other deep switches). For those dissatisfied with the button change-up, it simply put window buttons back to the way they were.
If you're comfortable with gconf-editor, head to to the apps/metacity/general folder, select the button_layout item, and change the value there to menu:maximize,minimize,close. If you're in need of a visual and detailed walkthrough, Trevor has you covered at the post.
Move Window Buttons Back to the Right in Ubuntu 10.04 [How-To Geek]