We've used Iron Mountain's LiveVault service but found that it was only good for file level backups. We liked how it backed up every 15 minutes. It doesn't support Exchange 2007-10 and the web interface was very poor. Who else is everyone using? The most notable names in online backup such as Mozy and Carbonite don't really seem suitable for larger companies. We have SQL, Exchange and Sharepoint servers and are looking to virtualize in the near future. Until then bare metal restore capability would be nice. We are currently using Backup Exec 12.5 but that can be so troublesome at times. We have about 2 TB of data. 1TB is archival data.
Check out the top rated online backup companies: http://www.backupreview.info/2010/05/02/top-75-online-backup-companies-for-may-2010/