Apple has posted these details regarding AVCHD import for specific cameras.

"iMovie ?08 and Sony HDR-CX11, HDRCX12, HDR-SR1 and HDR-SR7 cameras work with AVCHD (high-definition) and MPEG-2 standard definition (SD) content when you follow these guidelines.

If the Sony HDR-CX11, HDRCX12, HDR-SR1, HDR-SR7 and HDR-SR12 cameras contain both HD (AVCHD) and SD (MPEG-2) content, iMovie ?08 can import the SD (MPEG-2) content. However, to import the HD (AVCHD) content to an Intel-based Mac, you must first erase the SD (MPEG-2) content on the camera."