Time _complexity_ is unchanged, but laziness makes it difficult to reason about when the time will be taken. This, more so than the space usage, is the reason laziness is avoided when run time is important.
> Strict evaluation is often a huge impediment to function reuse.
This reads like an argument for having laziness as a language construct, rather than for having it as a default.
Lazy evaluation can make space usage difficult to reason about, but time complexity should be unchanged.
Lazy evaluation, by default, is also a huge benefit to Haskell. Strict evaluation is often a huge impediment to function reuse.