Sometimes, yes - more often they result in cronyism and officials and bureaucrats amassing power to trade for $$.

Since you brought up trains, look at the giant mess that is the California 'bullet' train. Not a single section of track has been completed, and it's already doubled in budget, reduced dramatically in speed (current projections put the trip time at ~4hrs due to a number of issues including track sharing), with ticket prices 70% higher than promised, and the legal requirements for private investment have been ignored because no private company is willing to touch it with a ten foot pole.

Dramatic changes indeed...

However for every Apollo, there's a dozen Solyndras.

Hmmm, looks like the US Government made the money back from that one. As a whole, American Recovery and Reinvestment Act of 2009 is MAKING money from the loans.

Even Solyndras is just one tiny failure in a massive pool of wealth-creation with regards to the entire program. US Government makes money from the loans. US citizens created jobs for each other. Solar energy development got accelerated.

The only answer to Solyndras is... damn, that was a single battle lost (0.5 Billion loan default), but the US definitely "won the war" on the $800 Billion program.