No Follow Affiliate Links

I have been reading up on using no follow tags on affiliate links on your wordpress sites as Google does not like too much affiliate linking.
Firstly what is your opinion on this, do you no follow every affiliate link on your site?
Will this make a difference to your ranking?
I have a large authority site that has hundreds of links out to products i am promoting / reviewing should i no-follow these?. If so is there a plug in that will change them easily and save time?

i'd like to know also

me needs to know it also..