Check Menneisyys' review at his
blog. According to him, Sprite's currently got some problems with synchronized Exchange Data, so keep that in mind. If you need the incremental backups or Network Backup capability, Sprite's your only choice.
If you just want a backup program, SPB works as well - and costs a bit less, with the ability to create stand-alone images... which the WM5-compatible Sprite no longer lets you create, from what I recall, although you could have Sprite installed on the storage card and run it from there, even after a hard reset.