iBackup is a relatively recent arrival in the online backup market but is aggressively priced and marketed. I haven't used it (I have used various and my current is InStorm - www.instorm.co.uk). iBackup appears to have all the key features you should require although it doesn't appear to be flexible in terms of retention periods (i.e. if you want to hold a monthly backup for the last 6 months). It does hold 30 previous versions though, which is better than many.
Online backups are brilliant for simple file restores and getting your data offsite. The thing to consider is your DR scenario - if you have to get a lot of data back across limited bandwidth it will take a long time (iBackup does systemstate backups so you should be able to start with a dummy operating system, restores systemstate and then restore data so that you don't need to reinstall apps).
