Speaking from personal experience, JustCloud is very shady.
I tried to cancel their service after 3 months of use. There's no link to cancel anywhere on their site! I emailed support, they gave me the runaround and 7 automated emails that asked why I was canceling. I was pulling my hair out just to cancel the f'ing account.
Despite these issues, the actual backup process was fairly straightforward and it even accommodates files as large as 3GB. But I just can't trust a site that gives you such a hard time canceling.
Also, the free trial really gives you very little space, so it's basically good enough if you want to see how the backup process works.