We are moving down from Brisbane and are considering settling in Warrandyte

Okay...

Warrandyte is a nice suburb :) It's in Melbourne's north-eastern suburbs (so a relatively affluent and highly sought after areas of the urban area). Many younger demographics these days and high Asian population more to the south around Box Hill, etc. I'm sure you've heard Melbourne is a very multi-cultural city!

Traffic: Well it will be no surprise to you, especially for a city with 4.5+ million people like Melbourne and Sydney. Think Brisbane but three times worse?
Anyway you won't be experiencing the most chronic congestion in the city, HOWEVER the network of arterial roads around Heidelberg/Templestow/Manningham/Doncaster (those North-Eastern suburbs)... Can become lengthy traffic queues - especially the morning peak. Try to look up Google Maos traffic and look at typical traffic for weekday peaks. Other major roads are worse than others. As you make your way down towards the freeway, you'll find more bottlenecks and much higher traffic movements.

The Eastern Fwy is the major arterial serving Melbourne's eastern suburbs :) It is congested during the morning and afternoon peaks unfortunately and this is the most likely route you'll be taking into the city, once you've made your way down from Warrandyte.
If you've heard of Melbourne's multi-billion 'East West Link' tunnel/toll road project and all the controversy surrounding it (still to be confirmed even now)... That is why! Because the Eastern Fwy is really the last of Melbourne's vast freeway network that abruptly ends on the fridge of the inner-city (Hoddle St / Alexandra Pde) and inbound quickly becomes a LITERAL 'car park' (all 6 running lanes) from around 7:15am right through to around 10:30am before it eases :O
Congestion further back on the Eastern, between Springvale Rd and the Bulleen Rd bend starts around 6:15am BUT isn't as bumper-to-bumper as the city exits.
You can expect an approximate average trip INTO the city each weekday morning, of around 60-90min (give or take)? Home not as bad, still a lengthy traffic queue outbound between the Chandler Hwy and Bulleen Rd. Around 45-60min home?
AVOID the following roads: Upper Heidelberg Rd, Lwr Heidelberg Rd, Rosanna Rd, Banksia St, Heidelberg Rd, Chandler Hwy, Bulleen Rd, Mannignham Rd, Williamsons Rd, Porter St, Burke Rd, Thompsons Rd. The Maroondah Hwy/Whitehorse Rd, etc are also very busy.

You'll no doubt be taking some of the above roads though! The Eastern Fwy is still your most direct (and probably quickest route), however as mentioned - still very heavy and allow extra travel time.

(e.g.) Start work @ 9am? Leave around 7:30am...

Any other Q's?

Great answer from Brad21. Warrandyte is very nice and I love that is has some of the best places to visit, tourists visit so that says something. Olivigna Winery is a must. People buy here for the large blocks and you feel like you are far removed from the city (yes in peak hour) but on weekends not so bad. You might want to try Donvale. I have lived in Templestowe too but that is getting very expensive. Donvale has surprised us, it is so close to the Eastern freeway, the Pines Shopping is very close and lots of great schools if that is important for you. I do make a point of leaving for work around 6 if I want low traffic. You get to the city early, you have an early coffee!