I'm sure Brandon will make an official post, but this is on the developer blog: Connect IQ 3.0.1 Now Available.
There is a new eclipse plugin, so be sure to grab that too.
The new Heart Beat Intervals feature in CIQ 3 does not work on Vivoactive 3 even though this device is listed as supported in CIQ 3. This seems to be due to lack of a 3.0 VM for the device. Is such a VM expected?
The Heart Beat Intervals feature works fine in the simulator. Test app:
https://github.com/vtrifonov-esfiddle/TestHeartBeatIntervals
In the simulator, Position.Info.when always return the same (constant) value, be it when simulating data or replaying a real-life FIT file