2-3 days ago I tested the microphone on an A500 with the latest updates. The volume was very very low. Today I bought one and the first thing I did was to test the microphone. No firmware update or Android update. The microphone volume was perfectly fine. I then updated the firmware and Android to 3.1 Tested the microphone and it was as low as the other tablet. So it looks like the problem is not material but software. It's either the Acer firmware or the 3.1 Android update that screwed the mic's volume.