Although I admit that I love to work on my bikes, I highly recommend a wax based lubricant for the commuter machine, not because it is better lube (although it is great), but because it is cleaner and tends not to ruin your pants like oil does. I highly recommend white lightning. I only apply it every month or so after the initial cleaning and lube.
In terms of other maintanance, fuss a bit with shifting only because I am anal about it and cannot stand imperfection in shifting. Brakes, once installed properly, are almost a no brainer unless you take the wheel off or are wearing down the pads.
Overall, I find that a well put-together bike needs very little maintanence to get the job done safely, but some maintanance makes riding much more enjoyable.
Oh and it probably goes without saying that those who leave their bikes in the rain have poorly-performing machines in no time at all. That is not to say that you cannot ride in the rain, but rust is sneaky stuff and tends to jam cables quickly.