Since our last visit 12 years ago, a limitation on numbers and improvements to the track and huts have meant an even better experience. Our recommendations would be: 1. take your time and don't race through it, 2. cook in the huts and get to meet the other walkers, 3. include Pine Valley and its side trips (Labyrinth and Acropolis) as part of your trip, 4. be prepared for all weather and MUD (it's part of the mystique of the Overland track), 5. the side trips are part of the track...take your time and do them all, 6. go outside during the night with your headlamp and check out the wildlife (wombats at Pelion), and 7. test out all of your equipment prior to the trip.
We really liked the improvements at Pelion (worth staying a couple of nights) and Windy Ridge (the viewing platform is excellent although the hut is a bit soul-less).
Wish we were back there already!!