Yes, this has been discussed before and no, this is not a bluetooth earpiece volume issue.

I encourage every owner who feels that the volume levels for the phone earpiece and the speakerphone are unacceptably low to post messages to the palmone forum in this thread:

Mine are unacceptably low to the point I can almost only use the phone with the wired earpiece.
This thread has nothing to do with the Bluetooth headset volume issue.
This was not an issue with my 600. It was awesome!
Please join that forum and express your displeasure with this obvious hardware issue with some units.