I have a Harmony 659, and although I use it nearly exclusively to control my lowly system (receiver, dvd, cd changer, hdtv tuner, computer), the direction pad is not ideal. I would have preferred a joystick. I also find myself scrolling through long list of functions to find obscure, but useful functions-- the 659 doesn't have enough hard buttons for all the functions. There are other remotes in the product lineup that have the joystick, more buttons besides, but I can't afford to upgrade to the 880.
The XBox 360 Harmony appears to be a slightly modified version of he 520, hwich has even fewer buttons than the 659.
I don't have a DVR (my god... the horror, the horror), but I'm led to understand that TIVOs have lots of useful buttons which aren't present on any harmony below the
688.
I haven't used the Sony 3100.
