My 2014 FLHTKSE had the usual puking of coolant and a thermostat drip. They fixed both early on and I'm now at 18,000 miles with no issues other than my right front speaker stopped playing.
I didn't know there was any "bugs" or consistent problems with the 14 models except for that ugly *** hole they put in the front of the batwing
The 2014 model year for the touring bikes was the introduction of the impacts from Project Rushmore. Depending on the bike, there were a number of changes introduced, which resulted in some "bugs", depending on which bike and when it was built. The bike the OP is asking about was impacted the most. There were several recalls- at least two on the clutch, (one was a do not ride), some issues with the twin cooling, brake line routing, and the saddlebag retention were all recall points. The Boom audio infotainment system has had several software upgrades addressing issues there.
Knowing all this, I could understand why someone would be asking the question. Owning the model of bike, I can say in my case at least the recalls were done and never impacted the bike's operation except for my dropped saddlebag.
As far as the mail slot being ugly, simply a matter of opinion. What I can tell you is that it works- that vent cuts back significantly on turbulence behind the windshield. Great design move, in my opinion.