I've tried a few of them but like the VZW holster/case combo the best of all for carrying around in my line of work (construction mgr).
Problem with the VZW holster/case combo is the extended battery with cover does not work. Also tried the Best Buy Platinum case for the x. It works with the extended battery, but it doesn't offer enough screen protection in a dusty environment, takes two hands to get the phone out, and it is too easy to put it back in wrong, risking a drop.
Best solution thus far for me with an extended battery is to leave the battery cover off and use VZW's "high gloss silicone case" with the holster from the holster/case combo.
This offers a fairly well sealed case that keep the dust out, slides into the holster with a fit that is tight enough to offer screen protection from dust, and easy to pull out.
I would like to find a holster/case combo that works with the extended battery, and does not have that top clip on the holster that takes two hands to get the phone out ... sooner or later someone has to come up with one.