I've been a Meraki MX user since Nov '14 and I think it's a great product but it lacked a community for it's users to collaborate on the direction we want the product to go in with new features. I want this to get the attention of Meraki and hopefully they'll join us in implementing these features.
1/4/16 Update: Meraki has begun responding to various posts!
Right now this site running on the free version of UserEcho so it doesn't have some features I'd like it to have (such as tagging).
Rob Geoghan
rgeoghan {at} gmail.com

Port mirroring on firewalls

Show resource usage on MS devices in Dashboard
Meraki MS switches don't provide any information on how much RAM, CPU, etc are being consumed, which is important for troubleshooting and sizing your deployment.
I know that if you call support, Meraki support reps can see and will provide average CPU load readouts over the last 1, 3, and 15 minutes.
Related: https://merakiusers.userecho.com/topic/621581-show-resource-usage-on-the-mx-devices/

Display up time percentages of WAN connections

Improved use of Brightcloud reputation service
Yesterday a spam message got through with a link to a domain that came up as suspicious according to (http://www.brightcloud.com/tools/url-ip-lookup.php) This link wasn't blocked by the MX. The MX should have the ability to make settings that are based on that tools various reporting results. The URL in question was 0 months old. To me that's a huge red flag that you shouldn't visit the site. I'd like to block "new" domains like this.

Ability to set WAN DNS servers with a dynamic WAN IP

Ability to search the event logs across all (multiple) networks

ISP subscribed bandwidth monitor

Browse test from Meraki on MX.

Improve RMA process with MX devices

Improved firewall settings to block specific IP address and range
Customer support service by UserEcho