I picked up a new bass in April that came with a bent pin. The guy who must owned it for me must have been a giant so I didn't use it for a while. A couple months ago I cut it down to a decent length so I could sit and stand with it.
What I find useful about sitting:
It conveniently places the bass in a manner that makes it easy to both play on the E string all the way down the extension, and all the way to the last note on my fingerboard. You do have to get used to it and find the right height to make sure you aren't straining any muscles in your back and shoulders.
In my opinion this is where it really comes in to play. The angle is just right for me since I'm quite short. Instead of stepping back and changing the angle of the bass to play in the upper register, it sets you up for that right of the bat.
Also I've heard that oak bent pins "sound the best". I think that really depends on your bass and the quality of sound it already makes.
My bass opens up just a bit when I use the bent pins for solos- and my pin is oak and graphite.