I bought the version of Torchlight for Macintosh, and it will not work, at all. I wouldn't be upset, except that I've tried asking for technical support three times in the last week, and have received no reply thus far. Is it always this bad, and if so, is there a way to get my money back somehow?

I can't say for sure if the technical support always takes its time to answer ...
But there exists a garanty to get your money back! I've never used it, but I think that there is information about it in the FAQ section of the site. It works if you bought the game less than thirty days ago.

In 30 days from purchase you can ask to get your money back, yes. And about waiting for response... well... It takes time, yes, but they always answer. Maybe their busy right now... Send them one ticket and wait.

No, don't send more tickets, you'll get pushed back in the queue. Just make sure you received the confirmation message and wait for support to get back to you. They're pretty swamped at the moment due to the influx of TW3 players and the Galaxy Beta, so it will take several days (one week from your last mail wouldn't be unheard of).