I share FlipFlop's experience. I've used my Canadian Tire SuperCycle SC1800 to commute for a year and a half now, up to almost 4,000 Km. I like riding the bike, but it needs a ongoing attention... regular drivetrain cleaning, a few replaced spokes. I even replaced the rear wheel and tires after a couple of thousand Km. But I keep riding it. The frame looks good and it's a comfortable geometry for me and, best of all, it looks so cheap and crappy I know nobody will steal it. I do have a replacement bike ready to go, a Giant Boulder, the lowest-end, entry level Giant from a few years back, very basic. It's a much higher quality bike (cost more than twice as much as the SC1800), but it's not as comfortable, so I'm hoping to make the SuperCycle last... even if I have to keep repairing it.

On the plus side, the ongoing repairs have resulted in a good box of bike tools, and increased my bike repair skills... I now do all the repairs on my good bikes, too. Haven't been to a bike-shop for repairs in two years.