I had a Pronto, played with it for a good while but I found a few deficiendies that just killed it for my needs. I ended up buying a Harmony. edgrood's post echos a lot of my own sentiments.
The whole Pronto programming scheme and ProntoEdit are overly complex. That can be a good or bad thing depending on what you're trying to do. It was a bit too much for me and I'm an engineer. I also found the contrast and readability to be lousy even with a backlight. The processor is slow and takes a while to change to a new screen. Lastly the remote is clunky, huge, and not easy to operate by feel in a dark room.
On the other hand the Harmony was an excellent 'out of box experience'. I was able to set it up quickly and it by far the easiest remote I've ever used or setup. While it is not ultimately as flexible to the extent of the Prono, it should be able to accomplish 98% of what anyone would need to do for a LOT less hassle
