Depends on your location really. If the trains from your location are anything like the trains from my location, getting a full size bike on in rush hour could be a pain. The trains are getting worse in terms of over crowding on the line I use, I've lived out of the city centre for just over a year now, I used to get a seat on the train most days, now I can barely get in the carriage and a couple of times I've not been able to get on and had to wait for the next train! If there are any delays, the situation is far worse. I see a bloke take his folder on though, so he manages.
Coming back out of the city in the evening could well be worse than the way in, some of the trains going out of the city between 5-6pm are utterly bonkers!