It doesn't suck. Everyone has their reasons why they like it or hate it, but it's a good cartridge and very efficient.
I cut my teeth on the .40 and I've always like it. Do I feel it offers more than the 9mm or .45? Well not in factory configuration. A lot don't like the recoil of the .40, but putting it in perspective, its recoil isn't an issue. Maybe it's because I'm used to shooting big bore revolvers, but I've never had an issue with .40 recoil.
People post charts of how the 9mm, .40, .45 all perform about the same, and they sure can, but it's because premium JHP ammo is designed to meet certain perimeters. In other words, they're designed to perform similarly. It's no wonder the 9mm guys say there is very little difference. Overall, the .40 has a lot more potential than the 9mm.
It's not a magical bullet, but put a .40 bullet where it needs to and it'll be very effective. Miss and there are no guarantees.
Glocks and Revolvers