I got this awesome plugin to work for my subdomain multisite install.
I am using WP 3.4 and wp-piwik 0.9.5, Everything's fine other then-
1- I have filled Piwik URL (REST API) & Auth token. I get You do not have sufficient permissions to access this page. when i try to save settings network wide as Super-Admin for wp-piwik under settings menu.
URL- http://example.com/wp-admin/network/settings.php?page=wp-piwik/wp-piwik.php&tab=homepage OR piwik OR tracking OR views
Not to worry settings get saved thou.
2- I get Piwik error: Please specify a value for 'idSite'. on my subdomain site's Piwik dashboard unless they are visited.
3- I am planning for a large network of blogs. I was hoping this would work fine with SharDB, HyperDB, MultiDB etc. I will try them and let you know soon :)
4- Also any update on this when you said on a post
Super admin stats select box is not perfect solution if you are using WP-Piwik in a very big netowrk. This was mentioned before and will be fixed by paging or a similar solution.
Disabling sitewide stats (dropdown) for Super Admins would be great.