We have the RDR-160 on our 69 337D. It is very cool. Ours is monochrome.
On our trip to the Bahamas, we flew "behind" several storms. They went left, we went right. Coming back, we picked up some strong returns, and deviated around them. It will pick up strong storms, that don't necessarily have lightning in them. Ours has the ability to point the dish down, in mapping mode, and I have used that several times to point out terrain, or find some place.
When I took my wife to Beaver Island, it was VFR, but the haze was so thick, you couldn't see 2 miles. I used the radar to find Beaver Island. (I don't have GPS, and the NDB on the island is out of service) Same thing when we went into Meigs. ATC had us going here and there, vectoring us around. With Radar we could pick up the buildings in Chicago, as well as the water inlets on the lake, helping to establish position.
The emitter tube on ours was replaced a few years ago, and we replaced the power supply this year. One point the shop made was if you have it in standby, you are still powering the emitter tube, and it has a finite life, like a light bulb.
You can get used, refurbished systems from
www.avionix.com
When out power supply went, I thought about picking up a whole new display, but it was cheaper (not by much) to fix the power supply.
Parts are available, and I think it is a very useful and valuable tool.