The best one I've had is the blackhawk serpa holster. It's got a hard plastic shell, and a gun retention system that is superior to everything. The tab on the side needs just a little pressure to release it, and the tab is placed so your trigger finger is in ready position. Without that little pressure on that tab, that fucken gun isn't coming out. It also comes with everything to use as either a belt or paddle holster. I used the paddle and a tight belt.
More info:
http://www.blackhawk.com/product/SERPA-CQC-wCarbon-Fiber-Finish,1144,1410.htmWith my new PPS, blackhawk doesn't make, and doesn't seem to want to make a holster for it, so I had to find something else.
My new holster is a galco leather deal. It's basic, and has no thumb breaks or any of that bullshit that's stupid as fuck. When you need to shoot someone, the last thing you need is a button and a strap in your way. The galco was spendy, but without the blackhawk available it's the only holster (style) I'd be willing to carry with.
The blackhawk was around $60, and the galco was about $100. Those prices compared to my fondness of both should be switched around, but whatever. There's many of the galco style xd holsters available, I believe even made by Springfield.