I'm running Hustle on a multisite network and after updating to 3.0.4 my site immediately went down with an error:
Fatal error: Cannot declare class SendGrid\Email, because the name is already in use in /public/assets/plugins/sendgrid-email-delivery-simplified/vendor/sendgrid-php/SendGrid/Email.php on line 5
It looks like the SendGrid plugin (http://wordpress.org/plugins/sendgrid-email-delivery-simplified/) and Hustle's SendGrid integration are both using the same library files and the class is being declared twice as a result.
Not placing the blame on WPMUDev necessarily (I'd expect that both plugins would try to detect something like this), just wanted to point out the incompatibility.
Due to load order (on my site at least) there may not be much you could do anyway since it appears that the SendGrid plugin's version of the class is the one loading and conflicting after yours is already in place.