Is "warm" a compliment or a criticism?

I agree. It's all a matter of perspective.

I like women with curves, but I know some guys that like women with "boyish" figures. I don't get that at all, but to each his own.

Isn't "hot" better than "warm"?

In theory, the objective of high-end audio is to reproduce the sound on a recording as accurately as possible. Hence, if the recording has a "warm" quality, that is what should be reproduced by a good system. Likewise, if a recording has a rather cool or analytical quality, that's what should be heard.

People being human, however, there are different "tastes" in reproduced sound. Some folks really like detailed, analytical sound (which, to my ear, often does not sound realistic), while others want to feel enveloped by warm, inviting sound. These preferences for sound quality used to be associated with the "solid state" camp versus the "tube" camp, but the best high-end audio gear today offers the best of both. I think that the term "warm" is used today to suggest the kind of sound that has some emphasis on the upper bass and mid-range, which is the portion of the audible sound spectrum where the human ear is the most sensitive (and, not so coincidentally, the range of the human voice).

Better "warm" than "cold". Better slightly "warm" than hard, steely, over-detailed with pinpoint imaging, tiring over extended periods, etc.

Regards,

I always think of it in terms of temperature, because music is a lot about how it makes you feel: Cold and lifeless, cool and distant, warm and sluggish, hot and irritating; yet, it can also be cool and collected or warm and inviting etc. There's a fine line between the different temperatures/descriptions and I think one thing to keep in mind is that the opposite of warm is not cold but cool. Since our own temperature fluctuates, what is warm one day can seem cool the next and viceversa. So that's another reason to seek a neutral balance (I don't care too much about reproducing what is exactly on the record). I usually prefer my drums to be relatively hot and electronic instruments to be relatively cold, but woodwinds have to be warm (if not either the player sucks, the recording sucks, or my system sucks :P). But this comes naturally. That to me is the whole point of being accurate. You have to screw up to make a warm sounding instrument sound cold.