I got a question similar to this one at my mathematical poker talk last week: Would you recommend professional poker or grad school to people graduating with a math major?
The answer certainly depends on the individual. Five or ten years ago, poker was much easier and if you liked the game and studied it for a few weeks you could probably beat the players in the casino. The games in the casinos (as well as online) have gotten much tougher since then, and it really takes a lot of work to develop the skill to make over $5/hour now.
Having never been to grad school, it would be difficult for me to say whether it's a good decision. Obviously, I'm planning to quit poker in order to begin grad school, so in my case I decided that grad school is probably the best option for me. However, this doesn't mean that I think I should have gone straight to grad school out of college. If I had done that, I don't think I would have known why I wanted to go to grad school, which might have made it difficult to motivate myself into being a good student.
For me, the desire to go to grad school developed over a number of years of feeling more and more socially irrelevant. Swarthmore encourages social consciousness, and I guess this might have rubbed off on me a bit. Over the years, the feeling that I could be doing something more worthwhile with my analytical abilities has been gnawing at me. As I've become more politically conscious, my desire to try to make a difference has really increased. I'm not sure that grad school is necessarily the ideal way for me to make myself more relevant to society, but I think it is a reasonable enough way to get started on that path.
That's more or less how I answered the question during the talk. Let me now expand on my answer a bit. The lifestyle of a poker player has many benefits that I could document, but the bottom line is that it can be very stressful if you don't have BOTH the right mindset and the ability to win comfortably. It also helps to be financially stable from the outset. I had the good fortune to have no debt and in fact quite a bit of savings when I started. I also happen to have an ideal temperament for poker: I don't get at all upset or angry about bad luck. This is part of what I mean by having the "right mindset." The right mindset also includes focusing on making good decisions as opposed to focusing on your financial results. Basically, having the right mindset involves adjusting your perception of money in order to subordinate its importance to the importance of good strategic play. Even if you have the ability to have right mindset, though, it's not going to work unless you are also a substantial long-run winning player. If you're just barely a +EV player, I think it's going to wear on you. A $1000 loss is going to take an average of 200 hours to make up if you only win $5 an hour. That is likely to be stressful even if you are predisposed to having the mindset to focus on strategy instead of results.
For me, poker was an ideal way to take a step back after college and a short stint at a sort of dreary job and decide how I wanted to proceed with my life. Some people may be able to do this while working for a year or two, and some people may already have it figured out by the time they graduate from college. One big change for me (and it may have something to do with getting married and having a kid) was that I decided it was worth the extra work and stress in order to have a greater impact on society. Different people may come to different conclusions on this point in different points in their lives, but now when I look at people who dedicate their lives to poker, part of me is surprised that they aren't plagued by the same sense of irrelevance that haunted me the past few years.