Like usual, you should read ExaBGP's CHANGELOG before upgrading but as some of the entries are not really obvious, here is a longer explanation of what to expect as this version introduces some non-backward compatible changes.
The version was bumped from 3.2 to 3.3 to reflect that some of the API messages format were changed. Therefore please check your code if you use the feature before upgrading.
In order to allow the detection of the change, the JSON format version was upgraded to "3.3.0" and is now using as version the release number were the last incompatible change was introduced.
For the JSON encoder :
In order to help parsing, the as-path does not return a list of list ( with first the as-path and then the as-set ). as-set is not a very well known feature of the as-path attribute, therefore it made sense to split both information and have both an as-path and an as-set, each as a simple list.
As well, most NLRI in an update will share the same next-hop (unless you have an implementation creating weird multi-protocol messages), therefore it made sense to remove the next-hop from the NLRI and to group all NLRI by next-hop.
As EOR (End of RIB) messages have no next-hop, they are under a "null" next-hop to keep things logically grouped.
When sending "raw" information about messages, ExaBGP now group the information under "message" and not "update" as it was a misnomer.
With those changes, I believe the JSON encoder will soon loose its "experimental" status.
For the TEXT encoder :
EOR are now encoded with "announced eor <afi #>/<safi #>", loosing the word "route" before "eor".
A few fixes made it to this release which means that even as it is a "dot zero" it is still the most stable release of ExaBGP.
Among the fixes, recent changes meant that next-hop were missing from route parsed (a nasty bug).
The multiple neighbor feature had no test suite and was not working as expected, this was corrected
Some change during the 3.x series meant that ExaBGP was always using multi protocol encoding to generate EOR. All vendors support MP but it was not great as it caused interop issues with OpenBGPD therefore the EOR for IPv4/Unicast was changed to not use MP.
And once again, thank you to those of you who took the time to report bugs or feature requests on the issue tracker.
All the best for 2014 ..