I think the category pages are the fun pages, these are the pages where you can begin to ease up on 'googlization' - Yes let your main pages work for Google - ease off for categories. and on the sub pages have some fun.
if you ever type your email address into Google - it always finds it on a sub page.
If you type in a miss spelling it always finds it on a sub page.

I think the further away from your main page - the better the long tail searches work.

Ease off, for Categories, loosen up for sub categories. have some fun with sub-sub categories.

(useless information) I have one user who travels and is not greatly web-intuitive. he uses other peoples computers including nephews, aunts, business acquaintances. so I wrote his dogs name on his favourite page (classified adverts) I added 'fatpup' to the end of the dogs name . . Now this user simply tells the computer owner 9 wherever he is, to type this word into Google. . this finds the page every time.

Giving words to Google to play with, is not as important as giving your users some "words"
Google is merely a tool. . Your user is the real item. Aim carefully at your real target.

__________________