As someone who has been forced to work with on a social web-app using smarty, I find myself asking co-workers to "just kill me now". Hey atleast I'm having a fun time moving all the business logic those smart smarty guys from India put in...right? no more, No but seriously, kill it with fire.
And caching..on disk, who cares? In general, dO we not have better, faster and more versitile options that would in any way justify a choice for smarty?
But, you can make just as readable code without smarty and load times are much faster (although smarty does have a caching system).