I have a collection of different recorders for weddings and I find that they can drift out of sync over time (long speeches) so I did a test.

I set up a GH2 filming the computer screen with a speaking clock and ran it for an hour. I also set up the following recorders

Results
GH2 01:00:01:13
Olympus voice recorder VN 8100PC 01:00:01:02
Tascam DR05 01:00:01:10
Olympus voice recorder WS-110 00:59:57:04
Olympus voice recorder WS400 S 01:00:01:02
Zoom H1 01:00:01:03
Tascam DR60D 01:00:00:24

I've written the percentage change on the back of each recorder and hopefully that will save me some time in the edit.