I also bought the Harmony 650. Take2 did not have stock of the 600 and I did not want to wait
First impression is amazing, I use it to control my TV, sound system, xbox and media PC (running XBMC).
For my XBMC PC I bought a cheap R99 remote, and naturally the Harmony did not set it up correctly, but wait, there is more. Learn IR! All I had to do is press each button on my old remote so that the software can learn them, and then map them to where I need it.
Now I have extra buttons on my old remote that are not linked to anything specific on my new remote and I plan to change the keymaps in XBMC to do new actions based on those keys
The Harmony 300 and 300i are great options if you only want one activity, but I must admit the activities are what make this remote brilliant.
I would highly recommend the Harmony 600 or 650