Here's my 2 cents worth.
Last Tuesday I travelled on The Overland for the first time, from Southern Cross to Adelaide. Then on Monday this week, I returned to Melbourne again on The Overland. Both trains were fully booked up (2 Red class carriages and 2 Red Premium class carriages + the cafe car). My main motivation was to do the trip and see the railway sights while I still could.
Overall I would say the experience was good, a bit more of an adventure than flying yet without the stress of driving. If I just wanted to get to Adelaide as quick as possible, I would obviously fly, and if I wanted to do it as cheaply as possible, I would have driven myself, forget the coach, I just wouldn't do that to myself.
That's not to say it couldn't be better, aside from the rough ride (particularly between Ararat and Serviceton) which was commented on by quite a few in my Red Premium class carriage on the return trip from Adelaide (this is more of a comment on the quality of the track itself rather than the carriages), the carriages could do with a bit of re-vitalisation. Wifi and USB charging ports positioned near the seat would be a good start, also the Premium seats don't really have the sort of premium feel that the more discerning traveller may expect, something a bit more akin to a modern business class seat is what I think many people may expect, rather than what was more like a business class seat from an Ansett plane from the late 80s.
That said, it certainly had its good points too. There is a good deal of space, unlike on a coach or an airliner, I never felt like I was sitting in a sardine can. Also, the staff were very friendly, and the catering was certainly better than anything you will find on a full service domestic flight (the curry of the day was quite good).
So while the positives are there and shouldn't be completely ignored, if the train is going to stick around, it could do with a bit of an upgrade to keep up with its competitors.
As for the comments earlier in this thread about nobody using this service, both ways The Overland was completely full. If the amenities could be improved, and more importantly, the frequency was upped to something a bit more user-friendly, I do think it could become more popular. While I did pay full freight for my premium class seats, I can't say for certain everybody else did or didn't.
Would I travel on The Overland again in the future? Probably, if it was timed conveniently enough, otherwise I would just drive myself.
Could V/Line run it? Of course they could, but the Journey Beyond staff did make the trip that bit more special, I can't see V/Line staff matching that. Maybe I am wrong.
I do hope it is going around again next year, or better yet, for many years to come after receiving a bit of love. Leaving it as it isn't going to help it grow.