The other night I decided to splash out (a tenner - last of the big spenders) and bought a new route, so now I have Cowlairs. It looked fairly straightforward at first, but I soon found myself in a rather harassed state when the morning peak kicked in!
The bi-directional signalling in and out of Queen Street can be quite tricky, and I've found that I'm having to stick to one line in and one line out in order to maintain any sanity, although this isn't obviously how it was designed. It doesn't help that platforming appears to be a bit random and less predictable than on other sims I've played, but I'll probably get used to this over time.
Overall, I'd say it's challenging, but quite enjoyable and I'll probably get a few more hours in over the weekend.