I can share two sets of experiences. One is in our
reference theater. We have a set of JBL amplifiers powering our bi-amped fronts and side/surround channels. They are conventional linear designs but made for pro environment with forced air cooling and such. It is nice for rackmount work as they do not need any spacing between them. Down side is fan noise. You can see them stacked here with their blue lights lining up:
The sound quite nice and super dynamic given our horn-based JBL Synthesis speakers.
I suspect though you are asking about the switching/high-efficiency designs. We sell a ton of Crown amps. Believe it or not, most of them go into homes powering whole house audio. We like them because we can get units with DSP, letting us optimize the response of in-wall, in-ceiling speakers. They too have fans but it is temperature/load sensitive. Even there, you would need to place them outside as they would be too noisy otherwise.
I have compared the higher-end Crown amp against our Mark Levinson amps. Against the Mark Levinson 532 Reference, the Crown had more powerful bass. Its higher efficiency means it sucks more power out of the wall socket, enabling it push the large Revel Salon 2 speakers I tested better. On the high-end though, the Mark Levinson pulled ahead. Hard to describe but the high frequencies are just not as clear. The Mark Levinson 53 which is a high-speed version of a switchmode amplifier (effective switching frequency of 4 Mhz), matched the crown and has delightful high frequency response giving best of both worlds. But it is, far, far more expensive.
An interesting hybrid new option is the new Lexicon DD-8:
http://www.lexicon.com/Products/Details/13
This is also a switchmode design but very compact and fanless. It gives you 8 channels, each at 125 watts, yet is in a tiny chassis and as mentioned, dead quiet. Its origins are in building amps that were light and efficient for cars. So Harman got together with TI and designed a highly integrated core amplification chip. We now use these in many whole house distribution environments. I have not done much side-by-side comparisons but just listening to them with Revels, they sounded pretty good. I am tempted to use them in my theater to bi-amp some of my channels.