If I took the train
I once worked this out to try to save money. I have moved further from a train station now, so these figures are not accurate any more.
If I took the train to work, I would need to be on the first applicable train from my local station, at about 6am. I would need to change 3 times, and would arrive at the station nearest where I work at 9:30am, giving a total of 3 and a half hours travelling. The situation is the same on the way back. Therefore, I have spent a total of 7 hours out of my day, nearly a full working day, just travelling.
If I could work on the train, then things become a little better. Time I could work on the train, taking into account the changes and some time to get set up on the train, would be approx 2.5 hours each way. Assuming I can get a suitable seat, of course. This then leaves me with only 2.5 hours to do at work, but it leaves you thinking "Why didn't I just work from home in the first place?"
In the car, the journey takes me 30-45mins. It makes for a simple choice.
Specifically with respect to these trains, one of the often-quoted advantages to using public transport is the ability to get work and/or other things done while travelling, which you cannot do while driving (at least, you shouldn't, although I know a few people who check their emails, update client notes etc. while driving). If there is barely enough space for you to sit, there is no chance of you being able to get your laptop out.