I have been told, by a former boss* that the true "high end" sakes are served chilled.
The lesser ones are served warmed, traditionally in a cedar/pine box (Can't recall at the moment - brain needs more coffee). The aroma from the box apparently helps mask some of the imperfections.
That said, I've had and enjoyed both. I've ready about how to make it as well, but have no desire to try as it seems far more involved than I'd want to try.
I do like it though, and we usually get the little sampler flights when we go to the sushi bar.
* - BTW, his name was Okuda and he's back in Japan now. So I figure he was a fairly reliable source
Your boss was right. The L.A. area is the largest Japanese "city" outside of Japan, and we have some truly awesome Japanese restaurants here, including several of the highest-rated restaurants in the entire Zagat survey, plus hundreds of small places that specialize in sushi, udon (noodles), and traditional fare.
My wife and I are not big fans of sushi, but my daughter is, so we go to fairly high-end Japanese restaurants with her for special occasions now and then, where we order "old fashioned" Japanese dishes, such as sukiyaki, tempura, etc., while they eat outrageously expensive concoctions of raw seafood and rice.
In the olden days I always got hot sake with my dinner because that's all that was offered, but now the good stuff is available in the U.S. The last time we went out together (Father's Day, a place called Kaya Sushi in El Segundo
www.kayasushi.com), I ordered a tasting sampler of four small servings of the restaurant's better sake offerings, which I think was about $20 - $24 (individual full servings run from about $16 to $30 for the good stuff, $8 for the cheaper sake that's served hot).
All four of the sakes in the sampler were served cold, and the waiter suggested that I try them in a specific order, from the mildest to the strongest flavor. Hot sake is pretty boring stuff, always the same, but this stuff had an amazing range of flavors and textures, some dryer than others, one -- my favorite of the four -- was actually white and almost creamy.
All four were both interesting and enjoyable and went very well with the excellent food. I'll order it again, but probably the sampler as I don't know enough about it yet to make a reasoned choice.
. I don't know much about sake (a little strong for me), but I have had a little plum wine at the end of a good Chinese meal, sort of like dessert. I love the stuff, but it tends to make me a little crazy 
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