I ride to work a couple days a week. I live on the Northside and work on the Southside. I ride into the CBD, catch the train to vaguely near work, then ride the rest of the way. Around a 53Km round trip.
The ride into the CBD from where I live (near Brookside) is pretty straight-forward. Get onto the Kedron Brook bike path, turn off to the Grange, then through Wilston and the back of Herston, eventually joining the Roma St Parklands route. Actually, just follow this route from Mitchelton to the CBD.
The rest of the route on this map is from the CBD to Archerfield, but I don't do this longer ride on a regular basis - just too damn hot at the moment.
The ride to the CBD is very pleasant. Mostly bike path with a few little-used back streets. There's only two higher-traffic roads - Kedron Brook Rd through Wilston, and Herston Rd through Herston. Kedron Brook Rd is nice and wide and has a marked bike lane. So does Herston Rd, so you really should be set.
There's a slight change that I need to make to this map. Basically as you go down Noble St, the council have added a new bridge to take you onto the back streets of Herston. Instead of turning left off Noble St onto the narrow pathway, follow the road around to the right, then get onto the new bridge. You'll know it when you see it. It also keeps you off B!tchy Hill (see my comments on the bikely map!).
Now that I think of it, I just recorded the new improved route with my iPhone's GPS just the other day.. *sigh* Check it out here.
Anyway.. I hope that helps!
Max