I'm a firm believer that it's better to throw more CPU power at a performance problem than to make code less maintainable. Just buy a faster server.
That hardly applies to library developers, though. They don't have control over their users' CPU power...
You should write the best good you can but I think maintainability is more important than performance (within reason). You can't help if some of your users are trying to run your code on a 486. You can buy a pretty nice server for $3000 these days. That's within almost any business's range.
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Michael McGlothlin
Southwest Plumbing Supply