cslinger, not to make things more complex, but how do you feel about elaborating on sight options, barrel droop and under/side levers? Depending on what a first time buyer may end up doing in the long run, these factors could be considered so buyer's remorse doesn't come in to play.
Sights are a personal thing. Scopes are far better for precision yet irons are a lot of fun for me. I have had Williams peeps on guns but currently I have a couple Air Force rear diopter setups on a gun or two. I have never used an electronic type sight on an airgun (Red Dot/Holo). The biggest caveat here is to make sure you get a spring rifle rated scope. (doesn't matter with PCP/CO2 etc.) Also if you are mounting to a powerful gun with lots of recoil use the scope stops.
I have only ever had one gun with a little barrel drop out of the box and I bent the barrel a tad to compensate. It is on a gun I never scoped so I don't even know how much difference it would have made to be honest.
As to break barrel vs.fixed barrel I have and enjoy both. The fixed barrels SHOULD offer more mechanical accuracy and are probably easier to shoot at a higher level but at my skill level its a moot point really. I find Weihrauch under levers to be very easy to cock where as I find Diana and Air Arms much more difficult. I don't have experience with side levers of any kind. Also, although you should keep control of the barrel/cocking lever at all times when loading a break barrel is more forgiving if it fails and snaps shut. It will break the gun most likely but your finger have far more leeway in terms of getting out of the way or not really getting caught. Fixed barrels, well they don't call em bear traps for nothing. If, in the unlikely event, the sear goes and drops the piston, swinging the lever closed closing the breech while you are loading......well think about a bag full of ice for your thumb and getting you and your severed digit to the ER. Point is ALWAYS keep control of the cocking mechanism so in the unfortunate even it gives way you slow it down/capture it enought to save yourself from injury and the gun from damage.
Honestly buying an air rifle for a first time shooter the best advice I can give is as follows.
-Buy quality. Spend the real money, you will get a REAL gun. Diana, Weihrauch, REAL Beeman's, Anschutz, Air Arms etc. I know this is a hard concept when we as, Americans, were brought up with BB guns being disposable toys.
-If you are a gun guy who has shot all their life, don't expect to pick up a spring gun of any kind and take to it like a fish to water. As a matter of fact if you have never shot before you are probably better off. Firearm skills don't translate to spring gun shooting (They do to PCP/C02). Spring gun skills, however will make you a better firearm shooter. The key is light hold, let it recoil. If benching, don't bench on a hard surface or bag, use a towel or similar.
-Buy good pellets. Crosman premier/H&N/JSB/RWS etc. Don't buy the cheapest Daisy branded pointed pellets you can find. Think of them like you would the crappiest steel cased ammo.
-Most Airguns need a little break in. A half a tin or so of pellets.
-DON'T GET HUNG UP ON POWER AND VELOCITY!!! If you are buying specifically to pest then, yes do a little research and get a power level that will humanely do what you want to do. That said the VAST majority of us want an indoor/back yard/convenient target shooting or plinking experience. Lower velocity tends to equate into easier to shoot, more accurate, much quieter, easier to cock and just much more pleasant to shoot. Just keep telling yourself when you are shopping and looking at velocity numbers or FPE......."WAIT A MINUTE.....I HAVE ACTUAL GUNS.....I JUST WANT TO TARGET SHOOT."
-Check your stock screws every now and then. If you start seeing a known quantity pellet start grouping erratically it is probably due to loose stock screws on a spring gun.
-Understand that air guns can be LOUD they don't just go pfffft. Spring or SSP guns are the quietest in general. CO2 and PCP can approach or exceed .22LR noise. For example I find C02 pistols uncomfortable to shoot inside, too much of a crack. The majority of the noise YOU will hear in a spring gun is the mechanical dropping of the piston and spring. The report tends to much quieter until you get to higher powered guns.
-DON'T USE FLAMMABLE TYPE OILS ETC. in the breech or barrel etc. Only use stuff like Pelgun oil and the like. Flammable oils etc. can detonate on shooting making a LOUD crack and possibly damaging the gun (It won't KABOOM or anything but it can be damaged).
Those are really the big things that come to mind. The biggest buyers remorse items I have seen or I have experienced center around buying too powerful of an airgun for what you actually want to do and buying too loud of an air gun that you cannot enjoy in the way you wanted, CO2 pistols indoors for me. That an the spring gun learning curve. Don't get frustrated, its not the gun its you learning a new discipline.
The other big thing I see as far as buyers regret is going cheap. Picking up whatever they have at Academy sports or Walmart or whatever. Almost invariably this causes most folks to dismiss airguns all together. Conversely when I have taken my airguns to the range I have dudes with $2000 worth of tricked out AR15s hand them to me so they can shoot my "BB Guns" They are amazed at how different they are from the toys they grew up with or bought their kid. My cousin grew up in a class 3 house hold and has shot more full auto and DD then most anybody I have ever met and had done so by the time he was 18. He came down to visit one year so we went to the range. I brought some of my more interesting toys for him, and I brought one of my air pistols for me........he ended up shooting my air pistol the whole time and just giggling saying that he hadn't had this much fun shooting since he could remember.
Most of all have fun with it but just like firearms ALL SAFETY RULES APPLY AT ALL TIMES with the one additional being WASH YOUR HANDS after every use just to be safe and get any lead off your fingers.
I don't wanna hear it. 
