I have about 25 years of experience using a full sized keyboard.  I'm not a heavy user by any stretch of the imagination but it's what I'm used to.  I rarely use insert or delete.  I use home, end, print screen, the arrow keys, and the number pad (including the mouse thumb number pad enter trick mentioned earlier) enough that I would missing having them.  I sometimes use page up and page down but not as often.  I've been toying with the idea of using something smaller.  I've had a full sized WASD with MX Brown switches for about three and a half years.  
I recently got an itch to have different keycaps and that got me looking into a wider world of keyboards.  I saw pictures of a 75% keyboard for the first time and right know I'm kind of infatuated with them.  I saw 60% keyboards and wondered how exactly those worked.  I saw pictures of GON's keyboards and was filled with keyboard lust.  I want to have a pretty easy time changing out keycaps on whatever I end up with.  I've been looking for a Keycool 84 to try out the 75% layout.  Then I saw someone selling a 60% GON with black switches for a very attractive price.  It's a NS38 instead of a NerD.  I've had it for a few days and I'm trying to learn what the function layer keys are.  I've found F1-F12, Grave mark/Tilda, the arrow keys, delete, home, end, and print screen.  I'm learning how often I use the keys that aren't on the main layer.  I'm not sure that 60% is right for me.  I'd like to give 75% a chance.  I'd like to give MX Clears/Ergo Clears a chance.  I'm still on the 60% learning curve.  I might go back, but I don't know if it will be back to a full sized.