I found the horizontal black leather case I have been looking all over for at Amazon - and it's 91% off. That's a benefit of having Apple release the new iPhone - most of the accessories for the original version are deeply discounted. I took a trip to the Apple store today and they had three cases to speak of - everything else was for the iPhone 3G.
So I came back and checked online it turned out to be a good thing that I did! With shipping this thing cost me $5!
I rarely wear my phone at my waist but there have definitely been times at the office where having a suitable case would have been helpful (e.g. when I am carrying my laptop and papers from meeting to meeting and am just out of hands).
Vertical cases don't work on most female forms (including mine) so having one that is situated horizontally will be a big help.