Spymasters spending a ot of time desperately trying to put you off getting the sleeper.
I've used the sleeper to/from Scotland twice in recent years, once on the Highland, once on the Lowland. My experiences are pretty reasonable
Overall I've found I sleep just as well in the seated bit than getting a bed. But, thats just me, we'll all be different here. I'm 6ft 5, the beds aren't really built with people my size in mind. But then again, nor are buses or planes.
If you're on the Highland, you WILL be woken up by the shuntaround they do when they split/join the train up at Edinburgh, however, nodding off in some anyplace bit of England and waking up to see the scenery is a lovely shock to the system.
As for the Glasgow sleeper, most of the train when I travelled was full of exiled Celtic fans returning south from a big European game. I don't think it mattered whether you had a bunk or were seated, singing was more of priority than sleeping. I suppose I could have managed a few hours otherwise.
The restaurant car thingy. Its OK, nothing really to write home about. Its also not the horror story that the above poster's stating.
The other alternatives book in advance and go in the daytime, East Coast (my preference) or West Coast (not my prefernce but still fine anyways). Most of these trains empty out a bit at Newcastle/Carlisle, and i always enjoy grabbing a cuppa and enjoying an hour of Northumbria coastline/Scottish Lowlands.
Oh yeah, and I know there's a few vintage train lovers here. The coaching stock is all Mk2's from the 80s, pulled by a class 90 from London, then double-headed class 73s into the highlands nowadays. To none-railway romantics, this = real train,with a loco and 15 coaches behind it