Well, honestly, I'm a person who doesn't even like transistor amplifiers!
That being said, I know quite a bit about class D amps and their strengths and weaknesses, and these comments apply to all of them. Overall, if somebody has normal modern speakers, I think a class D amplifier will sound just fine. The strength of class D is that they are extremely efficient (around 90% efficient while traditional class A/B amps are around 60% efficient), so they are not going to get as warm as a traditional amp. Also, since they are so efficient, the power supply for the amps (both the AC line in and the amp's DC power supply) are not taxed nearly as much. The DC power supply can be considerably smaller, and if the power supply is a traditional linear design, the power transformers can be smaller which saves weight and lowers excitation current losses. The amp will be quite a bit lighter since there is less heatsinking and the transformers are smaller.
One thing that doesn't get covered very much: Class D amplifiers are not strictly "digital". They are technically PWM (pulse width modulation) devices where the audio is converted to PWM in the analog domain. From that point, the signal goes to output MOSFETs and then to a passive low pass filter (an inductor) then to the speakers. The purpose of this inductor is to filter out the clock frequency which is used to determine the duty cycle of the PWM; its usually several hundered kHz.
That inductor is the source of the main of the disadvantage of a class D amplifier. Since it is basically a coil of wire in series with the full bandwidth of the audio, it has all the drawbacks which inductors within passive crossover networks possess. The resistance and impedance can react with the impedance of the speaker and cause frequency response errors. These are not going to be excessive with modern class D amps though, but they will be there. Also, since the the output filter has to be of a very low order (6dB per octave in some designs), the filtering is not very effective. This means two things; there is going to be a relatively high amount of leakage of the high frequency clock and the upper frequencies of the audio can be affected. The leakage of the clock frequencies is the bigger problem as far as I'm concerned as its energy which is always being fed to the speakers. Whether it effects the audio is debatable, but I would rather it not be there. If you look at the output of a class D amplifier on an oscilloscope, you will instantly see what I'm talking about. In fact, these amplifiers cannot even be measured by test equipment unless a special low pass filter (AES 17) is inserted before the test gear because the leakage overwhelms the measurement.
The bottom line as I see it would be; if you have average speakers with average to low sensitivity, then a class D amplifier will be fine and the clock leakage is of little consequence. If your speakers are very efficient (like any speaker which has a horn tweeter), then there is more likelihood that the clock leakage could be an audible problem, at least in my opinion. If your speakers have very low impedance and/or are a "difficult" load for an amplifier, then these are not a good candidate for a class D amplifier because of possible interaction with the output inductor in the class D amplifier.
