I purchased a Texas Deadlift bar from LiftingLarge.com. I haven't had a chance to use an Okie deadlift bar more than one time, but they are a bit whippier than even the Texas Deadlift bar. The customer service is poor and it WILL take a long time to get your bar. But the bar does give a bit more carryover.
I did a video on the Texas DL bar here:
Depending on your style of pulling, you'll probably get 25-50lbs out of it. In my opinion, there is no real reason to get one unless you're planning on competing in a powerlifting federation which allows them. The whole point of the bar is to make things easier and that makes it less efficient for actually getting strong.
But they're a fun toy. No doubt.