Well, I've had my Pro78 for two days now, and thought I would share my initial impressions, both good and bad.
Speaker and voice alerts are by far the best I have ever seen. The ONLY two detectors I haven't owned are the STi and the 9500i, so maybe they're better, don't know. I can't tell how many Bel Vectors and Express Series' detectors I have owned that blew the speaker out. For that reason alone I stay away from them. The speaker on the Pro78 really seems beefy, if that makes any sense. I have some hearing loss and Tone 3 really has ALOT of bass to it, and that makes for improved sound for me.
Mount and suction cups to me seem to be better than average. I wish it would incorporate a slide system, ala Valentine and Belscort. I will have to say that the suction cups, bar none, are the best I have used. I live on a dirt/rock road, and have to travel about 1/2 mile down a hill to get to the paved road. By far this detector, and to a certain extent the V1, seem to not shake up and down violently (which I would surmise would not be good for any electronic instrument). The Belscorts shake so violently that I generally don't even mount them until I get to pavement.
The blue display I really like. That really surprises me because I literally can't stand to look at the blue X50 display. For some reason it makes my eyes hurt, like a blinding light. Yes, even dimmed, it still hurts. I thought it may be replicated with the Pro78, but even at it's brightest setting, I can look at it without my eyes hurting. The "periscope" LEDs are a neat idea. I had wondered why, after all the improvements in RDs since the 1980's, the alert light is missing on nearly every detector. Remember the old orange lights of the Escort, and the orange or red lights the Unidens had depending on which band it was?
Build quality seems great. It doesn't have any seams that vary, and it seems midweight as far as holding it in your hand. I actually like the blue speaker covering with the metal gridwork behind it (I know I'm sounding like a Cobra owner).
Radar reception, quite obviously the most important factor, I am not yet sure about. The local supermarket has a K band transmitter on the door, and it is literally pointed straight at the ground. The Pro78 picked it up from the left side about 90 feet away, while picking it up from about 180 feet on the right side. I then tried my 1793SE, which I have only owned for about a week. The 1793SE beat it from the right by about 30 feet, and from the left about 50 feet. I then tried my Bel 795 (I know), and it was almost exactly the same as the 1793SE. I then later drove about 30 miles, and coming around a right hand turn the Pro78 alerted to K band. I clocked only .10 mile before two LEOs following each other went by me in the opposite side of the highway. I wasn't impressed with that encounter, and no they weren't IO, they were CO in the middle of a transport or something.
I will update later on more impressions. I am impressed with what Whistler is trying to do with the Pro78/XTR-690 class, competition will give us RD owners better products at lower prices.