From a business point of view I used the Glasgow sleeper because it allowed me to arrive in plenty of time for a 9am meeting, without having to get up at 4am to fly and hire a car. It gave me a full day to work in Glasgow if required. It also gave the benefit of the opportunity to do something interesting once meetings were over - although I accept that most business people wouldn't choose to take an evening trip to Corrour or climb a mountain at Pitlochry before getting the sleeper home.
The solution to this is for inconsiderate fools to stop organising 9am meetings for people who are travelling a long way. 10 or 10:30am is just fine, and has the advantage of the organiser having time to get in, have a coffee and prepare the room and meeting materials so the visitor's time is properly respected by everything being ready for their arrival rather than them showing up at 9 half asleep and then a load of faffing about ensuing. If you can't lose that hour, then either arrange for the visitor to have an overnight stay so they are awake for the work, or order in lunch and have a working lunch with a buffet to regain the time that way.
Not only is doing this contemptuous of the visitor, but it also means they won't be working at their optimum because they'll be tired, either because of a very early start or because of "sleeping" on the Sleeper, which for most people is never quite as good as a proper bed.
At the moment from Edinburgh it's an 0540 train for that, but if HS2 takes that to 0600 ish that's getting almost civilised and definitely preferable to me than the Sleeper (and no doubt way cheaper, too). 5 hours kip in a proper bed is way better for me than 7 fitful hours of sort-of-sleep.