For one of my Meraki infrastructures i use the normal SNMP checks. Configured SNMP inside dashboard for all devices and every device is queried like every other switch or router.
Works good - a little bit slow but ok 
For a second environment i wrote a special agent using the Meraki API.
It is working with a big “but” → hard query limit per second - this was done from my site before API v1.0 was released
I had no time to test the changed behavior after the 1.0 release.
The API is a nice approach if you want to monitor a world wide installation (this was my use case)