I figured this out about age 8 with my .22 caliber Benjamin and have been shooting lefty ever since. Now, it feels odd to try to shoot the gun right handed.
It's also why I've set my compound bow aside and taken up crossbows for bow season in Texas.
The biggest problem I find with lefty shooting is crossbolt safeties. THANKFULLY, I found a left hand safety for my Winchester 1400 at Numrich Arms some years back. I really prefer Mossberg's tang safety. My 20 gauge Spartan SxS has a tang safety just like my old Sarasqueta, BUT, SxSs including my Spartan, tend to be cast to the left for right hand shooters. Fortunately, it's a cheap SxS and the stock fit had enough slop in it I was able to shim the cast out of it and now it's cast neutral.
So, if you're a lefty, you REALLY need to try that double before you buy it. Repeaters are usually easily shimmed and are usually built cast neutral at any rate. There is a new O/U on the market, Benelli I think, that does not have an inletted tang, but whose stock is attached much as is a repeater. I've been interested in trying one of those, but it's sorta priced out of range for me, so it's not a holy quest or anything.
With pumps I'm a Mossberg or Browning kinda guy because of the safety.
I'd like to have a Mossberg 930 or 935 for waterfowl, but since I got the tang safety reversed on the Winchester, I haven't worried a lot about getting a new gun just because of the safety. Were I to actually BUY a new autoloader, though, that tang safety would sway the deal big time.
All in all, though, it's worth switching to the left so that you can actually SEE the target. Of course, that does mean there's one less excuse when you miss.