1. "we don't know if the reactors will save carbon over lifetime".
Surely this is better than strip-mining most of the ocean and asia for rare-earth metals for circuitry and/or batteries. (Li-ion ones will be needed at a local (and hyper-local) level to store supply/demand fluctuations from renewables).
2. "boogey man". This used to be something like "Nixon backed this over thorium-salt", or "something, something, nuclear-weapons". Here it's "big bill" himself.
The fact the gates foundation is investing in something should make the product be seen as common-sense, e.g. "in the future we need clean water". (And they want to be in a position to sell it back to you for nominal profit).
3. Bringing up long lead times.
Lets be honest a huge amount of this is public opinion/pressure and political manoeuvring. Nuclear as a word has all of the cold war rhetoric (from all sides) attached to it. If governments wanted Fission plants built within a decade it would happen. As it stands globally many factors are squeezing Nuclear construction projects due to their admittedly _very high_ up-front costs compared to technologies such as Wind.
The alternatives to starting this now and having it available in 10 years are, realistically, more coal plants. This is until renewables and energy storage take the next quantum step.
Wind, sun, wave and other renewables are only useful for non-baseline energy production until we invest in huge (normally gravity derived) batteries, and these take a long time to plan/construct/build infrastructure for.
4. Safety
Frankly I've always viewed this as a mute point. Had the Fukishima plant been in a country which doesn't have regular earthquakes/tsunamis it would still be 'just working'. Why the accident here should mean a plant in the lowlands of Germany (arbitrary geo-location) should close is entirely a political/posturing decision and not one based on science.
5. Not this article, but people mix the fusion/fission work into a mess.
Fusion has been bigger on promise than it's delivered so-far. But frankly this is a no-brainer small annual investment given the potential cost/benefit ratios for clean power, and frankly how close we now are.
Fission plants unfortunately do have nuclear waste. But then so do dead solar cells, dead lithium batteries, aged coal plants. There is nothing for free. But, when the nuclear waste can be captured in nice small drums and put at the bottom of a disused mine-shaft and sealed off from the environment isn't this the same ethos as carbon-(re-)capture on steroids?