Since this is a poo-storm I will add my two cents.
I believe that macbook or macbookpro should be there, as much as macbookair (if it exists), a tag synonym should encompass the same models (i.e. unibody, etc.)
The truth is that tags are nice, but if you go tooooooo specific, it turns against you. If I have a macbook pro 17’’ problem, I don’t think that the (in)existence of that tag would prevent me to find it. I’ll just search macbook pro 17’’ etc.
Apple Laptops are called macbook, macbook pro and macbook air. That’s all you need in my humble opinion. Of course Powerbook should be there too, but old models will definitely get less questions.
All other variants (size, etc.) should be grouped into synonyms.
And Unibody stuff?
Unibody should be its own tags. Mac-minis are unibodies too, so that’s an additional and distinctive feature of a particular model. There are Macbook Pros and Unibody Macbook Pros. The tag should exist as such.
In my opinion, (to repeat myself) the current Apple models (macbooks) are more or less the same and a problem that exists on a Macbook Pro 15’’ will probably be the same on a 17’’ model and if not, my idea is that Tags are not the right tool to differentiate that particular aspect of the question.