One of my gripes about Citylink is that they dont serve Edinburgh Airport. I used to have get the express bus in to town to a roundabout on the outskirts of Edinburgh to pick up the Fort William bus (fortunately there was a macdonalds for breakfast).
Sadly the Fort William bus has gone so fly to Inverness now.
I find it odd that many buses don't serve the airport to be honest I don't know if it is a case of BAA charging them too much for the honour or if the operators consider the time penalty too much. Even the local buses don't bother! Places like Stirling, Dundee, Linlithgow (or anywhere to the North or West of Edinburgh have to either drive or double back which is not ideal!)
I would be good to see some more buses looping around the airport, I know when the tram is working it may not be as bad for many, but that is still someway off an people would probably still prefer a direct bus to changing onto a tram.
Back to Edinburgh - Glasgow.
I find it difficult to see a 24 hour demand, but I also find it hard to know where the line should be drawn. a 0030 service in both directions would have a lot of customers but the train will probably not be that nice afterwards and the depot staff will need to put a lot of work in to bring it back into a standard to carry passengers the next day.
To me the big missing point is an earlier departure in the morning, say 0450 so people can get the 0550 Edinburgh - KX service. I have used the first trains each directions and they are not badly loaded by the time they get to Linlithgow and Croy. Once Eureka comes also I hope the Scotrail timetable see's some adjustments to make use of the improvements on the ECML. For example the current first train from Stirling arrives at Waverley at 0624, which would be too late for the 0625 proposed service to Kings Cross. Lets hope Scotrail can move the service so it arrives at 0615 instead!