We live in Coorparoo (next door to Holland Park) and hubby gets an express bus at the top of our street which then gets on the busway. It takes only about 15 minutes to the city.
The busway picks up further out, and there is a pick up at Holland Park (and others further out) and they would have a good run too I imagine, but I'm not sure how far out the separate busway runs. Transinfo would be worth a call, as they would be able to tell you times and more detail.
If I have driven him to work at peak time, it would take maybe up to 30 minutes in very heavy traffic but not often would it take that long. We are only getting on the freeway at Cornwall/Juliette Street, so we only catch the last bit of congestion before it hits the city. Non-peak trips to get to the city take only six or eight minutes, so we do avoid peak time.
Someone else who travels in from further out will hopefully help you with that question, but Holland Park and surrounding areas are a very quick trip, especially if you can pick up an express bus that gets onto the busway.