I'll like the TimeSpanPicker besides the localization issue (mentioned [url=http://www.telerik.com/community/forums/windows-phone/timepicker-and-timeselector/localization-issue.aspx
]here[/url]) and a UI confussion.
If you define the MinValue and MaxValue (say 5 minutes and 5 hours) and you open the picker you'll see the hours looping goes to 9999 hours. That's crazy! You can't select these but if can't use them in any case why show them? Can you limit the items in the separate lists to the minimum values that must be available? That would be great and improve the usability of the control!
I think the most critical part is the hour looping list. The other lists should get limited if you can clearly say what items must get shown through the combinations of MinValue, MaxValue and Step.