I went into a local Walmart yesterday and looked at ammo. The shelves were pretty picked over, with 9mm, 45 and 38 completely gone. There was a modest amount of 40 and 380 available, so I bought some of each as I have those calibers in guns. My plan is to shoot 9mm, 45 and 38 less if it is going to be scarce, and 40, 22 and 380 more. I like to shoot and can be pretty happy shooting any caliber.
I have 3 guns in 40 and like them all - a Sig P229, a Glock 23 and an H&K USP 40c. The Sig is the heaviest and most fun to shoot because it handles recoil so well.