In the recent past, I've spent a decent amount of time commuting by train. I've used Caltrain (which is fine), Bart (which is usually nicer) and even both (which is... less nice).<p>I've actually found the train ride to be <i>valuable</i>. It gave me an hour or two a day of uninterrupted time when I could focus on what <i>I</i> wanted to do: either work on my side projects or read books.<p>In the recent past, I've been too busy to read much fiction; having time on a train which was "useless" anyhow let me get back into it. I enjoyed a whole bunch of fantasy and SF novels thanks to having a commute. This is where something like a Kindle <i>really</i> helps: it's light and convenient enough to read even if I can't get a seat, and I can carry as many books at once as I want. It also let me re-read the Wheel of Time series on the train, which would not have been practical with hardcover (or even paperback) copies of the books :P.<p>If I did manage to get a seat--and, since I often travelled at off-peak hours, I usually did--I had other options as well. For one, I could work on my own projects. This was particularly nice because I had a very limited amount of time, say exactly 40 minutes. This helped me focus on specific tasks, like fixing some bugs, that would have been less interesting if I was planning to work for several hours at home.<p>Another option was reading non-fiction. I actually learned a good deal about theoretical CS, programming languages and type theory last summer. Partly, this was because I was working at an awesome startup; however, reading academic material on the train also helped immensely. Since the train had less distractions than virtually anywhere else I spend time, I was able to get through denser passages without any compulsions to do something else (like go on HN :P).<p>I've also found the train a good place to read CS papers; since the time I can spend on it is inherently limited, it helps me get a quick overview that is neither too deep nor too shallow. Given an unbounded amount of time, I tend to either quickly skim a paper and get distracted or spend far too much time thinking about particular details. Reading something on a train helps me get a holistic and useful first impression.<p>One thing I've learned from experience: if at all possible, avoid transfers. This is especially bad between different services like Caltrain and Bart, but even Bart's timed transfers are decidedly sub-optimal. Two 20-minute chunks with a five-minute break in the middle are <i>significantly</i> less useful than a single 40-minute chunk. Also, knowing you will have to get up to transfer soon definitely creates more of an overhead for opening your laptop or getting a book out of your bag.<p>Anyhow, in total, I'm actually pretty happy if I can commute by train. Even though it does take up a fair amount of time, the time can actually be useful. I've even found the constraints make me more productive for certain things than just having that time at home.