I'm mainly focusing on the P229 chambered in 9mm, but I'll take other experiences (P226, SIG Pro, etc.) as well.  Don't worry about recommending to me other calibers, I will get those in time.  Right now I would preferably like to hear from people that own 9mm SIGs and have fired +P as well as +P+ ammo to see how well the guns have held up over time.  Not a dealbreaker, but just something in my head I wanted to get answered.  I know the manual says something about just going all the way up to +P, but want to know how far these handguns can be pushed in real life...and I won't be using high pressure loads all the time, especially for punching paper.  Thanks!

Sig P228's and P226's are issued to the US military, as well as the British SAS, and 9mm NATO is +P to +P+.  SEAL's chose the P226 because of the increased durability over the Beretta.  If you replace the recoil spring ever 5k, and the rest of the springs every 10k, it will last longer than you will.

Well...I've owned a 226 and 229 in .357 SIG and shot .357 SIG +Ps through them with no problem at all.  I suspect you'll be fine doing that, though I can't speak for the 9mm specifically.

My department, until recently, issued Sig P226 to all their deputies and issued +P+round as the duty ammo.  There was little or no parts breakage with those weapons.  The Sig line of handguns will stand up without issue to +P+ loads all day long.  

Considering the 229 was built from the ground up to handle the higher pressures of the .40 it is a bit over built for the 9mm. The 229 is probibly the strongest 9mm/40 made. The gun will no doubt out last you.