I continue to use the free version and have less than 100mb of total storage online (2gb is provided Free), – I have been VERY happy with it. Again, I am using it for backup of key invoices, documents and backup files from my business software. I’m not using it for music, video or photos (I’d use a hard drive and TimeMachine for a full system backup of these files – 100GB).
If you are a Home user, but using it in a more corporate or business environment (server backups or backup of folders over a network) you will NEED to update from Home to a Pro version. If you are like me and just backing up files and folders on your computer, no worries – keep on going (make sure you are running 1.2.0 – the latest version from Mozy).