This is a recommended upgrade. There are no backwards-breaking changes, only bug-fixes and enhancements.
Enhancements
Added MongoDB::BSON::looks_like_number flag.
The Perl driver has always been coy about turning strings into numbers. If you would like aggressive number parsing (if it looks like a number, send it to the DB as a number), you can set MongoDB::BSON::looks_like_number to 1 (defaults to 0, the previous behavior). See the MongoDB::DataTypes pod for more info.
Tests should now clean up after themselves, leaving no test databases behind.
Bug Fixes
Setting a sort in the arguments to MongoDB::Collection::find is now passed through correctly to the cursor.
Fixed segmentation fault in array serialization: caused by specifying an _id field on insert and using an array (not a hash or Tie::IxHash).
Fixed segmentation fault in threading: if Mouse was used instead of Moose, version 0.43 of the driver would segfault if multiple threads were used.
MongoDB::Cursor now inherits the $Mongo::Cursor::slave_okay global setting, as well as checking if slave_okay is set on the cursor instance.
Fix GridFS functions to only ensure GridFS indexes on writes, allowing GridFS API usage on slaves.