I commute from Glasgow to Edinburgh for work and for the most part it's ok.
My main gripes are:
1/ The cost of it. Astronomical pricing to travel between the two biggest cities in the country. Sadly there's no choice but to suck it up. It is particularly bitter when you pay a fortune and end up travelling on a train that's freezing, damp and looks like it was nicked out the transport museum.
2/ Minimal carriages at rush hour. Take last Friday for example. I leave work and go and get the train just after 5 o'clock between Waverley & Glasgow. Understandably a very high demand route at that time of day. The train pulls up, lo and behold two carriages. This resulted in the carriages that were there being absolutely packed. I ended up sat on the luggage rack for half the journey, people standing the whole length of
the carriage.
Edit to add: FWIW it's better than First Great Western who I had to use when I was away with work. They're a fucking shambles. And I won't even get started on the bus service from Arriva The Shires.