Yes, the difference is noticeable, especially in the lower gears.
I had an ASP UDP on for a little over 3 years, but swapped it out for a DMD. I noticed the loss of power going to the DMD. It was worth it, though, because the harshness of the vibrations at higher RPM was driving me nuts. Now it is sooooo smoooooth.
I haven't heard of a specific failure related to a UDP, and I have not had any problems related to the use of mine after 50K miles. I am not an expert on this, but my impression from everything I've read is that the DMD was developed mainly for NVH (Noise Vibration Harshness) reasons and possibly because of destructive crank harmonics.
It's your choice, now that you are aware of the risks of possibly destroying your engine.
-Lance
