putting aside the boxy shape, plastic feel, and generally butt-ugly appearance- and thats a lot to put aside- the main thing to me is that the angle of the grip to the barrel is just wrong.
ya, I know. I remember when they came out and they made all the claims of ergonomically superior, more natural grip, blah blah. maybe it's even true, maybe it is a better way to go, it's still wrong.
at close distances (the kind where you'd use a pistol) you should be able to pick a pistol up, point it at what you want to hit and have the bullet end up reasonable close to where you intended, without aiming.
pick up one of those dummy rounds with the laser in them (intended for bore-sighting I'd imagine) and try it out. a dart board from across your living room works well. I've only had the rounds for 9mm and .45LC and have tried it with a S&W 6906, Ruger Vaquero, browning hi-power, and a glock maybe a dozen or so tries with each gun.
except for the glock all where solidly within the triple ring on the dart board, most within 3 inches of center, the glock was off the board for the first 2 or three times, better on the last few but still crap.
it's fine for accurate when you take the time to aim carefully, but it never feels natural or a fluid action to aim and fire one. I have better groups with most other guns but not a huge difference.
I think it mostly comes down to the fact that I fired a lot of rounds through a lot of different guns before I ever touched a glock, it's different from what I'm used to so it's wrong.
most of the people I know who like the glocks started using them when they were fairly new to shooting pistols. I have even met a few guys who would call it their preferred gun, all three of them had a glock as their first pistol, and learned to shoot on it.
I'd imagine those guys get the same feel from a 'regular gun' that I get when I pick one of those ugly 9's that look like it was made by Mattel.