I now have a CaseTechWorks case. My thoughts:

The swivelling clip really isn't as big a deal as I thought. It does end up upside down every once in a while, but putting the case on teh clip is a lot easier because I can do it sideways.

Now that the leather is stretching, it closes easy though it was a pain at first.

The case adds some nice heft to the treo when I'm using it as a phone. It feels more like something I want to jam against my ear.

The window is even harder to see through with the case on. I used to read things through it all the time, using the scroller on the side to peruse AvantGo. Now, that is hopeless.

Overall, it's a good product.