i had the same issue,
but now it works fine...
TO HELP US :
activate patern on the galaxy gear
on your phone
FOR HANGOUT ONLY :
remove any SMS software (Go SMS, and others)
Because it was the problem for me... (but i will give you a solution after)
activate hangout SMS
Go to options, SMS, and activate Notifications and Vibrate
On the gear manager, go to Notification, more, and check "Hangout"
Go to Hangout, send a message to your own phone number to test it, and wait 1 or 2 minutes to validate if it's okay
FOR GO SMS :
Go to Hangout (if you have) and uncheck the SMS option
Go to GO SMS, settings, "advanced", and UNCHECK other SMS softwares in the section "other settings"
return in "settings", go to "notifications" , check "enable notifications"
go to "defaut notification settings" , and uncheck "vibrate"
Now you can use GO SMS on your phone and receive the notifications from the stock SMS software on your gear
The only one problem is you will receive 2 notifications on your phone, (but only one vibration)
Sorry if the paths and names are not the same in english for you, because my phone is set in French...
Cya