Last RC for 0.5.1 the release one will be out in a few days... So last last last chanse to repoort issues.
A few bugs have been fixed in the release for details check the change log.
How to Upgrade (from 0.5.0)
This is a drop-in replacement so most people will not notice an in-place upgrade. If you have an automated installer hopefully things will be better as it now works more reliably and you no longer need the MONITORING_TOOL=none and CONF_CAN_WRITE=1 keys for the installer to be written. So just fire up msiexec with your overrides and it should work as expected.
Another important change which might be worth noticing is that filters can no take multiple warn/crit/*. The reason for this is that some keywords are mutating (changes) noticeably count this means an expression like the following will not work correctly in 0.5.1:
..."filter=count = 4 OR value = 3"...
This is the same old bug which was "fixed" in 0.5.0 as well but there was a problem with the solution which has now been remedied.
In 0.5.1 what you can do is split the mutating expression from the non-mutating lie so:
..."filter=count = 4" "filter=value = 3"...
Changes (sine 0.5.0)
This is perhaps more interesting for developers of scripts for NSClient++ but it is a way to send notifications without having to adhere to the Nagios check result format. It was designed to make event-log to syslog forwarding simpler as well as detecting installed software and similar non check things. As of yet this can only be used inside internal scripts but the idea is to use these building-blocks to add many new features such as automatic monitoring configuration in the future.
The old restructured documentation has been replaced with a new one based on mark down. This is actually more important then it seems as markdown renders on github this means you can now easily edit the documentation directly in your browser if you see any issues. The documentation was also brought back into the regular git repository as well making this even simpler.
While the installer is not all that new enough of the logic has been rewritten and tested to make sure silent installers are very very easy to make. Overriding configuration keys on command line is now much more predictable and works without strange voodoo.
As always there are numerous bug fixes and additions and improvements for a full list of changes see the what's new section in the documentation.