It fixes many bugs, including performance issues, and newly have the following functionalities:
- Group mapping: an option to synchronize a Google group into Thunderbird address book,
- Disk cache: an option to flush memory data to a disk,
- Read only mode.
I've re-upload v0.5.50 since the previous one has a problem in locale packaging. Please download again if you download v0.5.50 before 24 March.