The .40 was really hot during the mid to late 90s. The bloom seems to be off now.
I have noticed when CDNN lists pistols for sale, .40 caliber seems to be $10-20 less than the same gun in 9mm. It is actually a perfectly good cartridge and I might would take advantage of the savings if I had the money to buy one now.
B/c the fbi went from 9mm, to 10mm, to 40cal.
Most other police depts followed.
It's tempting but that would be one additional caliber of ammo I'd have to stock up on, so I'll stick with the 9.
The .40 is a fine round. I think the industry screwed up in pushing the fact you can shoot the .40 (rather unpleasantly) out of a 9mm frame.
When you shoot it out of a dedicated .40 or over engineered frame, as the 320 seems to be, it is very pleasant and recovers nicely.