Looks good.

(Edit: also, I'm assuming the bottom side, or inner layer, has solid ground pour.)
(I tend to be verbose on explanations or critiques, so take this as high praise ... or at least a pat-on-the-back for following the appnote, which, I didn't look up this one specifically, but they usually show something very similar to this. It's pretty good.

)
I will note just two things and an optional third:
1. You may want an LC at the input there, to keep sharp edges out of the input cable. You have the flanking bypass caps which is great, but they still have some ESL which lets through some of the switching edge. The buck input side is a noisy place, because the current is fully switched, 100% on to off -- you might have, oh Idunno, 60dB of attenuation there (a factor of a thousand), but out of a ballpark 10V step, that's still enough mV to pick up on a nearby radio.
Typical would be just a 0.1 to 1uH inductor in series, and probably just one more of those ceramic caps at the connector.
Optional 3: you may want a TVS here, to prevent overvoltage, and maybe also a series diode to prevent reverse polarity. The problem is this: you plug in a DC adapter that's already charged to nominal 12V or whatever, and an inrush surge flows through the cable. The cable has maybe 1uH of inductance, so there is a series RLC circuit between the supply's bypass cap (something fairly large, 100s uF), the cable inductance and resistance, and your ceramic bypass caps (and their ESR). The fatality is this: the ceramic caps' capacitance drops sharply at high voltages, so instead of kicking to a peak of less than about 24V (as a linear capacitor would do: a film or electrolytic), the peak voltage can be 30, or 50 or even 100V, and that can easily damage the regulator.
So, just a SMAJ15A in parallel with the filter caps by the regulator, would be simple insurance for that. And for series polarity protection, a PMEG3020 or B130 or ES1B or whatever would be fine, or a P-ch FET if you need low voltage drop.
2. The diode is pretty huge -- 5A, but you're only using 2 of it. This saves a bit on conduction losses (although not really all that much, because the diode Vf curve is exponential), but likely will cost more on switching loss -- the 100s of pF (or is that into the nF, I forget) junction capacitance has to be charged with every cycle, and it adds up.
So, simply to say -- you may find higher efficiency with a smaller diode. And if you don't have high operating temps, don't be afraid of a relatively leaky diode (like the aforementioned PMEG family), they tend to have lower Vf.
(Still higher efficiency can be had from a synchronous type regulator. TI makes one that delivers 3A from a mere SOT-23!)
Okay, so maybe I got verbose as usual, anyway.

Cheers!
Tim