Rather than running continually in the background, and using its own scheduler, this is a Feature request for an option (command line ?) that causes Juice to Exit once it has checked and downloaded all subscriptions.
The usage pattern would then be to set Juice to check all subscriptions on being started, and have Juice run via the Windows Scheduled Tasks mechanism (i.e. cron under *nix)
I'm always in favor of making a program do what it does best (i.e. manage and download podcasts) and leave other tasks (like scheduling, playing podcasts etc') to other dedicated programs.
Regarding the scheduling, I think that avoiding running Juice in the background is a healthy thing.