In After Effects, speech metadata can help with syncing video and audio elements since speech metadata imports with layer markers with the transcription as labels. The preference for this feature is off by default (via); the toggle is under Preferences > Media & Disk Cache > Create Layer Markers from Footage XMP Metadata.
Depending on your success with a speech transcription in Premiere, in AE you might not even need to scrub with audio (CTL/COM +drag) to refine marker placement, as you would after using the asterisk key (*) on the numeric keypad during a RAM preview.
After Effects Help LiveDocs has additional details, for example:
"When you render and export a composition, you can write XMP metadata to the output file that includes all of the XMP metadata from the sources for that composition. This includes all of the composition markers and layer markers in the composition, all of the XMP metadata from the source files on which the layers in the composition are based, comments from the Comments columns in the Timeline panel and Project panel, and the project-level XMP metadata for the project in which the composition is contained. XMP metadata from nested compositions is recursively processed and included in the output.
[...] In addition to storing XMP metadata in After Effects project (.aep, .aepx) files and source documents used by Adobe applications (for example, .psd), After Effects can write XMP metadata directly into the files for many container formats [like MP4] ."
Of course this aspect of metadata piques the interest Flash developers like Brooks Andrus (Yes, the h.264 Specification is Freely Available), who shares some screencams from looking at MP4 files inside the Flex Debugger in The XMP Revolution is Here:
"...using XMP extends beyond standard file info and saving a video file’s editing history. Case in point, Premiere Pro CS4 has a killer 'speech to text' transcription feature. The transcription text is stored as XMP within the video file. This allows Premiere and other tools to accurately search for this data within a file (powers the search feature inside of Premiere and Bridge). As a special bonus, Flash Player 10 provides the same data in its onXMPData callback."