As a partner, I love that I can access all of my client accounts from one portal. I appreciate that clients don't have to share their password info with me, and that means I don't have to keep track of passwords, either! 🙂
As a regular user of CTCT, I love that I can store all of my branding colors for easy use so that I don't have to keep referencing style guides (both mine and my clients') to ensure that all branding colors are accurate!
