Hi, I live in Japan. Although I do agree with the answerer who said "It's worse than the Japanese media says," that's not saying a lot. The media in Japan is not really a watch-dog, muckraking media like we have (had?) in the West.
So yes, the media and the shady bureaucrats who run the country have not been as open about the disaster as they should be, but you're asking about travel.
A good guide for travel info the US State Dept. If they tell you not to go, don't go. But, check the link. There is not significant danger.
The immediate area of the radiation leak is fairly removed from just about any place in Japan you'd visit, unless you had plans to travel to Fukushima. Tokyo is relatively close, but it is still quite a distance from Tokyo. Other areas that tourists frequent, such as Kyoto, Osaka, Hiroshima, and Okinawa, are very far away.
People tend to think of Japan as a very small country where a disaster like Fukushima shuts the country down, but for nearly all of Japan, it's business as usual. Fukushima, again as has been mentioned, is in the Tohoku region, which tourists do not frequent. Not to make light of the disaster, but other areas including Tokyo go about their daily business, and vegetables, dairy products and other resources are produced country-wide, well out of range of the radiation in most cases.
However, the immediate area is probably worse than the authorities are letting on. But there is no need to travel anywhere near the affected areas. I was in Tokyo a few days ago, and really I saw no discernable dip in foreign tourists. (I did of course notice it in March and April.)
The main downside to traveling now, as gkanekoa mentioned, assuming you are coming from the USA, is that the Yen is extremely high compared to the dollar right now, so everything is quite pricey. Even if you find a bargain on a flight, the exchange rate and cost of everything inside Japan will be even more expensive than it usually is.