iMessage speech (applescript) timing out after upgrade to yosemite
I originally wrote:

This bug appears to be resolved in 10.10.2

****I was wrong ****

For me, the bogus timeout alerts seem to take longer to start after enabling a handler script than they did in 10.10.1, but they still happen and make the AppleScript handler feature unusable. By loading up my handler script with debugging code (logging everything) and tracing Messages with DTrace, I've nailed down beyond a doubt that the timeout alert is triggered for every event passed to the script within milliseconds of the event before the script itself is in control, blocking its execution.