Is program speed less important than safety? Sometimes it is – and sometimes speed is safety. A slow autopilot is a dangerous autopilot. That's why so much safety-critical software is written in the least safe programming languages.

A lot of programs aren't like autopilots – a slower, safer transaction processor is usually better. Google's early credit card charging disaster is my favorite example (it would never happen with a bounds-checked, garbage-collected language runtime).

However, there's the "counter-anecdote" of a cell phone company switching to a fancy new billing system which took more time to charge customers for calls than it took customers to make calls. It fell behind to the point where they had to avoid charging customers for a month worth of calls because they couldn't compute the right amounts. So sometimes trusting one's money to a slow program is rather unsafe.

And then there are high-frequency trading algorithms. Speaking of which: is speed less important than program correctness? Sometimes it is – and sometimes speed is correctness. A slower chess program playing under time control will settle for a worse move – a less correct move. Slower project scheduling software will come up with a worse schedule.

Life in general is a game played under time control. Often, "slower" means "being able to process less information in less ways" – in other words, dumber, further away from "correct".

What about time to market – isn't program speed less important than time to market? Sometimes it is – and sometimes higher speed is shorter time to market. A breathtaking game or special effect on today's hardware that others can only pull off on tomorrow's hardware means that the game or the special effect made it first to the market.

("Performance tricks" sound more relevant to the real-time world of games than to the offline rendering of movies; a great counter-example is procedural generation of outdoor landscape in Brave by Inigo Quilez.)

But time to market is also affected by development time; is program speed less important than development time? Sometimes it is – and sometimes higher speed is less development time. A developer waiting for slow programs develops more slowly – and developers often wait for their own programs (tools searching for stuff or summarizing stuff, build systems, tests, machine learning algorithms, …).

Another point is that a developer whose code tends to be too slow will waste time looking for a faster, fancier, buggier algorithm, sometimes sifting through many options, each of which could be fast enough if coded by someone else. A developer whose code tends to be fast the first time will move on to the next thing more quickly.

Is program speed less important than X? Sometimes it is – but sometimes speed is inseparable from X.