Units is a cool piece of software, but I have since switched to qalculate. Mostly units has some silly defaults like needing to type tempC(30) instead of 30C; and it's nice to have a full calculator.

I know it's a way to specify that the conversion is absolute rather than relative, but qalculate just asks you about it the first time you convert, and since converting oven and outside temperatures is most of what I do, I don't havr to bother with remembering a different syntax.

Also qalculate is an awesome piece of software in general, so if you're excited by units you should check it out!