Google Contacts 0.5.50b5 is now available for download. It fixes bugs in the previous beta and improves efficiency. In this beta, group mapping is changed. So, you need to set it again before you use it.
This will be the last beta for v0.5.50. Please let me know if you find any problems.
[Update] b5 has a problem in synchronizing contacts having non-ascii characters by batch mode. So, I'll release an addtional beta. It'll fix the issue and include some new functionalities.