I have not had any reliability problems with my Pronto Pro. The only time it has "frozen" is when the batteries are almost out and need to be recharged. In this case I have to press the reset button. If you make sure the batteries are properly charged then this should not be an issue.
Overall, I find it to be invaluable, having replaced all my other remotes and added X10 switches as an inexpensive way to control lighting. I also use the optional RF extender for kit that is not directly in the line of sight.
To get the best out of it you have to be prepared to spend some time using the Pronto Edit software which enable you to customise the interface.