I wouldn't call them ugly, but I wouldn't call them especially aesthetically pleasing either. The compact models look the best in my book as they look to have the best proportions. The sub compacts look a little too squished and stumpy and the full sized and long slide versions just look like a kid who hasn't quite grown into their excessively long arms and legs yet.
Function wise, I wouldn't hesitate to employ one to protect myself if I could find one that was comfortable in my hand, but that just hasn't happened. I've tried two 23's (a Gen. 2 and a Gen. 3), and I've fondled plenty of RTF Gen 3 and Gen 4 Glocks and I have the same problem with them every time...I just don't like the boxy profile of the grip. I like a more oval shaped grip like what I have with my 1911s, my P2000 and my Sigs.
All that said, I have a couple of dead nuts reliable go to 1911's that get the nod for personal protection, and if I need to stop a Maytag fridge sized intruder, I have long guns that will do the job much more effectively than any pistol.
At the end of the day, the Glock isn't particularly ugly nor is it particularly pretty, but it does its job. Even though it's not the right tool for me, it's certainly the right tool for many thousands upon thousands around the world.