To start with, the P220 Combat is a great looking gun. Pictures do not do it justice. It appears solidly made, with a definite feel of quality to it. Controls are solid with a positive feel, and are within easy reach of this particular right-handed shooter. The 10 round single-stack mag was not a huge compromise for me, because you cannot carry more than 10 rounds in California anyhow. It comes with a true M1913 Picatinny Rail, which is a plus for you accessory heads. When it's time to shoot, I've found the P220 Combat to have a sweet, sweet trigger. . .although not as easy for me to fire quickly as an XD45. The 3-dot sights are dialed-in pretty good, not requiring any adjustments to the combat sight picture and impact straight-and-true within practical self-defense distances (for longer distances, you might need to hold a little higher, but thats because we're dealing with a heavy 230gr bullet out of a 4.4 inch barrel).
For some negatives, I do not like the price of the pistol (you can get similar quality and utility at the 500-600 range. I currently am eyeing the Glock line of pistols). I do not like the Nitron finish (wears very easily, especially at the locking surfaces and around the barrel). I also found that I naturally shoot more consistently with pistols that have wider grips like many Glock models or the XD (I'm hoping new Hogue P220 grips will fix that problem, however).
For all its shortcomings, I feel that the P220 Combat is a gun I'll be keeping for life. And it'll be over those years of companionship that I hope to make back the high-dollar investment.