I think Hermione is extremely trustworthy. She used the Time Turner responsibly and never told anyone about it until it was absolutely necessary.
That's a good point. But she's not very truthful, even when there's no reason for lying. At least that was the case early in the series.
Of course, everyone is older than they were.
I wonder if we'll see that again. That's a pretty powerful piece of equipment, if you ask me, and it's pretty daring to had it over to a child, even one that appears as mature and intelligent as Hermione. And everything else seems to show up again (which, actually, I like -- I hate when series writers, for books or TV, create something fantastic and then just drop it and forget about it).