Been on both the Brisbane Sydney and the Sydney Melbourne. Fab journey, it's always late, but people shouldn't moan when theres a cracking view on the way.
The seats spin 180degrees so no one has to sit facing backwards. There is also a water cooler at each end of coaches. Interior wise, the buffet is very similar to the old BR miniature buffet. The coach door end panels are almost identical but the big surprise is the old BR HST light fittings. External doors are a bit different, with no drop windows. Food on board was good, about £6 for a decent (albeit microwaved) meal.
You do notice some rough riding for the first hour from Brisbane or first two hours from Melbourne. These bits are dual gauge and Brisbanes additional rail (narrower) or Melbournes additional rail (wider) cause a few bangs and bumps. The two main journeys the XPT does are fairly long, but doing the trip in daylight is possible in one direction.
My 14-day trek round Oz was Sydney-Melbourne-Adelaide-(flight)-Cairns-Brisbane-Sydney. (I'll never stay at that Melbourne hotel by Southern Cross again - squeaking trains on the curve all night). :roll:
I even ran into a very high up boss of RailCorp (Countrylink's owner) who suggested doing what he did and moving over from the UK. Still got his business card and seriously thinking about it now.