A bit of a mixed bag
What has probably given people in the know nightmares is that computer simulations of BWR failures show that small containment structures incorporating pressure suppression measures such as tanks, wet wells or ice condensors, offer much less security than the alternative design of a large heavy containment vessel. The small containments at Fukushima have a much greater risk of failing in the event of a catastrophic steam explosion or the high pressure ejection of the molten core - both of which could happen in a BWR.
The good news is, as Lewis points out, the production of energy in the reactor is rapidly diminishing, and with every hour the risk of further melting recedes. The reactors are slagged, but it looks like the vessels have held.
Where I disagree with Lewis is that the lesson of Fukushima is not to build more reactors now, it's to sit down and look at reactor designs and see if we need to learn lessons from this tragedy. Since we don't know the precise sequence of events that led to the loss of all off-site and on-site power for the pumps it is probably worth finding out what went wrong before proceding with new build. Fortunately we're not going to be building any more 1960s vintage reactor or containment designs; but that doesn't mean it isn't worth looking long and hard at what happened here and improving things further.
Right now, I'd be looking at CANDU reactors, not just because the Canadians are nice people, but because we could start building them as soon as possible, they work, they work well and they're safe.