I am currently evaluating QRecall. This is what I found in the logs after trying to merge:

Action 2012-10-30 11:15:48 -[PackageList sizeEstimate]: unrecognized selector sent to instance 0x11b345150
Action 2012-10-30 11:15:48 An internal program error occurred. Please report this problem to the developer.

Robby Phlig wrote:An internal program error occurred. Please report this problem to the developer.

Robby,

Please send a diagnostic report: Help > Send Report...

We'll review the details and get back to you.

Robby discovered a bug in the merge logic. The merge was failing to deal with items who's content had not changed, but who's metadata had and that metadata included a large amount (more than 20K) worth of extended attributes.

If anyone else is encountering this issue, you're welcome to download and install pre-release version 1.2.2(1):

Download the QRecall 1.2.2(1) disk image.
Open the disk image and launch the Install QRecall application.