I have been testing my sti-r+ in the horizontal position for a little while now after having it mounted vertically for sometime, though I haven't had any enounters I did notice a few things.
When driving by falses the detector can clearly see both frequencies from the automatic doors nearly 100% of the time. It rarely did this verticaly mounted, it would only see in most occasions the door opener frequency facing the road. Although it would sometimes detect falses from greater distances. Probably due to the polarization of different automatic doors?
Another thing it has improved dramatically is the way Autoscan works. It seems to filter out a $hit load more falses! I haven't locked out one yet, I don't use Autolock.
But detecting the real thing is where it counts and as mentioned above I'm yet to encounter a real threat yet. The reason why I mounted it verticaly to begin with was to detect low powered horizontally polarized photo radar.
So yeah I just thought I would share some of the things I noticed with you guys considering the vertical option.