According to Romans, it's a noble death. The Japanese consider it an honorable death, and/or a way to regain/preserve one's family honor.
The concept of honourable death has been misunderstood often, though. Seppuku is the act of final defiance. It basically says, "I would rather die than to serve my master's enemy". In many cases, they would commit seppuku even before a demand was given when they realize that victory is not going to be achieved. When this happens, they do it so that they won't be shamed through torture or public humiliation, as the people back then was known to do.
In some cases, the lord would ask them to commit seppuku to spare their family from execution, in a sentiment that symbolized the person's willingness to take responsibility, to repent and to take up the burden that would be on his family unto himself. Even to this day, we have people committing seppuku, but not through the sword. Japanese politicians caught with a scandal would always give their resignation letter as a way to take responsibility, and they would never become politician again as penance for the scandal, effectively killing their political career.
Similarly, modern-day honourable seppuku is also performed not out of selfishness, but out of responsibility. You do not commit suicide because life has been bad for you. You commit suicide when you rake up a large debt, been mooching off your aging parents, have no prospects and no future. In this way, you commit suicide so that your parents can disown you, and thus refuse to inherit your debts, no longer need to take care of you and no need to worry over you anymore. Similarly, there are parents who commit suicide when, in their minds, they think their children and spouse would be better off without them.
So it's a different kind of suicide compared to what people of other cultures perform. In Japanese culture, an honourable suicide is done for others, not for yourself. You do not commit suicide because life is hard, but because life would be harder for your family with you around.