Has anyone switched from Class AB/A to Class D? Was it better? Was it worse?

I've had class A/B amps from Denon, PS Audio, Vincent, and Krell.

Very happy with my class D PS Audio M1200 monoblocks.

@tomcarr ya, I was eyeing the Class D PS audio monoblocks. But it really stinks for me to buy them without hearing them. Even with the 30 day return period. Were able to hear them first before buying them? 

There are a few differences:

1. I don't think we really know how long class D amps will last, how they will most likely fail, or whether they can be maintained in the same sense as a conventional amp.  They could last longer.

2. Class D amps use far more complex designs.  Many of the amplifier boards are built as modules and used by multiple amp makers.  That's why a class D amp will often be identified as a Nilai, NCORE, Purifi, PASCAL, etc.  Some (all?) of these companies also build and sell compatible power supply boards.  Add a case, power switch, input buffer. wires & connectors, and you're done!  I don't think all class D amps are built this way, though.

3. The more recent introduction of GAN FETs has made for another family of class D amps.  I don't know if these are also mostly being based on modular sub-assemblies; what makes them distinct is the use of a specific kind of transistor.

None of these are necessarily negatives, just things that occurred to me recently.  Hopefully, @atmasphere will drop by and fill in the blanks (please?)

@tomcarr ya, I was eyeing the Class D PS audio monoblocks. But it really stinks for me to buy them without hearing them. Even with the 30 day return period. Were able to hear them first before buying them? 

I'm not Tom, but I also own the M1200 monoblocks.  A friend has them and I did get the opportunity to hear them a number of times before I bought them.  I needed more power than the class A/B monoblocks I had, which I loved and thought would be hard to beat for the money.

After a speaker change to some very power hungry speakers I decided to try the M1200s in my system.  They sound every bit as good as my previous amps and are able to deliver the power the new speakers wanted.  I have also owned the m700 amps, which were surprisingly good, but not as good as my previous amps or the m1200.  

There's always something "better" or "different" that might suit your tastes more than the m1200s, but they are very neutral, light, quiet, and have none of the negative traits I've experienced with other class D amps. 

As a bonus, you can roll the input tube.  I've tried a number of tubes in mine and like Amperex Orange Globe 6dj8 and Genalex Gold Lions the best.