I did a 3 day trip earlier this year, and hope to do another soon.
Some random suggestions that may help you...
They basically linked together existing trails, fire roads etc. so terrain is extremely variable based on what was there before. There is a lot of easy flat fire trail, the occasional bit of singletrack, but mixed in with some unrideable sandy/boggy bits, and killer climbs up washed out tracks that you have to push! Plenty of variety, and goes thru some stunning natural bush - you won't get bored.
Two of us had panniers and two had trailers - those of us with trailers found it
much easier going (too much weight on your back wheel, and a high centre of gravity is a recepie for disaster in sand/pea gravel!) Needs to be a single wheel jobby like a Bob Yak or Topeak Journeyman though, not your average two wheel commuting thing. About bike hire in Perth
http://aboutbikehire.com.au/ hire out Yak and Ibex (suspension) trailers specifically for the Minda Biddi. While we're on equipment, a hardtail is fine, but a duallie better.
Trail is well marked and huts well maintained - but do buy the maps to take with you.
I've been told the nicest bits are around Collie, but most people start in Perth and don't get that far - me included!
It gets very hot and dry in the WA bush during the summer, so not a good time to do it!
The huts are very basic, a shelf to lie on, so take sleeping bag and mat, and all your own food and cooking gear. There's usually a town every 2/3 days to re-stock food (and have a hot shower!). There are rainwater tanks at the huts, but you can't guarantee they'll be full, so especially if you're travelling at the end of the summer, bring sufficient water with you.
We found the distances most days too short for moderately fit adults, and were arriving at the huts by midday, so maybe worth trying to do more each day.
Never seems to get really crowded, we did it on a holiday weekend and were the only ones in the huts each night! There are occasionally large groups going thru, but they warn you about these on the Munda Biddi site - worth checking.
Overall, its a fantastic trail, and I can't believe more people don't do it - you'll have a great time!
