Bar End Shifters - Upside Down???

As I was in the process of installing the bar end shifters, I realized that they didn't look quite 'right' to me. Referring back to a catalog showing an built up Cervelo Dual, I noted that the shifters on that photo were pointed up. (I looked on the Cervelo website and found only pix of frames). I also recalled seeing other people ride bike with the shifters going up. I started a web search and I won't bother placing the links as I don't know that many of them will be valid for long, but I found shifters placed both ways on various brands of bikes. Most, based on my search, are pointing downward, like mine, which I believe is the technically 'correct' way. (Park tools backs me on this; and the Shimano lettering is facing the correct direction.) I have to admit that I haven't watched the pros that closely (or even noted how racks of TT bikes look in triathlons) to see what the 'norm' is. I will be looking at this from now on with more interest. I honestly do not know which will be easier to use. I have a feeling that it has as much to do with what you get used to as anything. And, I made the transition from twist shifter (Schwinn Sierra hybrid) to brake/thumb trigger (Shimano Sora/Tiagra) to brake/beside the lever (105; Ultegra; Dura Ace) without any difficulty, so I tend to think I can get used to about anything within reason. (I still regularly alternate between Sora and Dura Ace shifters.)
The drilling on my aero bars does make a variety of alignments possible. I could possibly even flip the extensions themselves (twisting the cables a little perhaps) if I wanted to try out the 'other way' without rerouting the cables. For this reason, I may wait until after a couple of rides before taping the bars or extensions.
I don't monitor bike forums or the like regularly, so I don't know what the thinking is on direction of the shifters. I will be keeping an eye out for more information about this, though. I should be getting some stuff together with the help of the local bike shop today (they are closed on Sunday/Monday) so I can make more progress on this.