i have both remotes - had the 659 first before getting the 676. the biggest difference is the 676 had additional page/ up down buttons - plus its a bit 'sturdier' than the 659. you can of course program the up/down for the LCD buttons on the 659.

what i don't like about the 676 is there is a circular ring around the select button for your directionals (up/down/left/right) and it is very very stiff to press. other than that (and without close inspection) that's what i see as the difference. i do notice i tend to inadvertantly hit the sound or picture button on the 676 when going for other buttons. i'm not sure if it's placement vs it just being a new remote for me.

btw-- i got the 676 at Sam's Club for $89

if you search these boards you'll see pictures for comparisons of all harmony remotes. for that price difference tho, i'd go with the 659.