Without ever having owned a SIG, or ever having a pistol's barrel recrowned, I can still confidently say that, if your gun is as accurate as you can shoot it, then leave well enough alone.

One normally has a barrel recrowned if its muzzle has been "dinged," or if the barrel has been shortened at the muzzle end, or if the rifling at the muzzle has been worn by cleaning-rod use.

I agree with Steve,if there's nothing wrong with it now don't worry.If it is or does get bunged up,have it recessed on a recrown to pull the bore back in for protection.The angle of the cut varies with the smith and the gun/caliber,so research your particular gun.Somewhere around 11 degrees seems about standard but those that persue ultimate accuracy have their own little setup with a certain barrel and crown in a certain gun type.

I sent my p226 .40 to sig custom shop back in august to get night sites and they happened to have a deal for $235 so i accepted it and got:

SRT Trigger
Siglite Night Sites
11' Barrel recrown
Action Enhancement Package
Feed ramp polish
Free VIP round trip overnight shipping (normally $ 55)
30% off any other services or accessories

When i got my p226 back the accuracy was AMAZING, the action enhancement package lightened my single and double action triggers to 3.5/7.5 lbs and made them feel smooth as silk, follow up shot accuracy is awesome with srt trigger. My P226 is now a tack driver when it comes to accuracy but with all the work i had done i cant say specifically how much the barrel recrown improved accuracy.

I just picked up a certified P239 9mm at a local gun show yesterday. I will be calling sig custom shop tomorrow to work out a similar deal to have all the same work done. Its well worth it!

I ended up having the shorter trigger, not the short reset as I liked mine as it is, the night sights and the re-crown. Should have it back in 10 days or so as it went out on Wed. past. My 226 had very smooth action and I like the trigger weight. Will let you all know how it comes back, hopefully before X-mas.
Be safe, Frank.