I LOVE the .40. I find it hilarious that many complain about the recoil, I'm not sure how old they are, but I'm in my mid-30's and have never shot anything shy of a .44 mag that I thought had any significant recoil. Ironic, because I am on the smaller side of things. I can easily get follow up shots and multiple targets with the .40. In fact, during my CCW class, I outshot 9mm style 1911's.
IMHO, the .40 offers the best BALANCE of all the handgun cartridges out there. To me, the 9mm is underwhelming, no matter how cheap the ammo. The .45 is great, but has no purpose in my lineup that the .40 doesn't fill perfectly. More capacity than a .45 with nearly or equivalent stopping power, all in a smaller frame gun that is lighter and easier to conceal. It is having your cake and eating it, too.
The cartridge itself is easily re-loaded and is amazingly versatile, shooting from 135 grain to 180 grain rounds with outstanding velocity. Once purchased, I can't envision the need for 9mm or .45. The .40 does it all. If I need bigger than the .40, I skip autoloaders and go straight to my other favorite handgun round, the .44 magnum. If I want smaller for pocket carry, a J-Frame is outstanding with .38+p. I will concede that I do occasionally utilize the .380, but that is EXCLUSIVELY based on pistol size and form factor. I never truly feel comfortable with it, and it is my wife's gun.
Honestly, I understand people skipping the .40 because of what they already own, but anyone who hates on the cartridge is either overly recoil sensitive or just doesn't want to accept that modern ammunition advances have lessened the appeal of the old stalwarts...