I use LogTen Pro but only on my Mac... don't use it on the iPhone/iPad anymore. Because of the user-customisable categories, I found that when I sync it often changes all sorts. Total hours are kept the same, but other things (such as private flying aeros time) gets wiped out each time I sync with an iOS device.
Heard good things about mccPilotLog though which I may try some time in the future and link it to my roster.