In a word

a few favorite terms from Dr. W's Miniature Lexicon of Efficient Critical Assaults:

arcane.
baroque.
braindead. A term from Ron Kuivila.
clear. Alvin Lucier: "I like my music clear. Like gin."
clever.
complex. Short for: "I don't want to get into an argument over which definition of complex is applicable to this piece. Not to be confused with complicated or hermetic.
complicated. I don't understand it, and don't expect it'll be worth the effort trying to understand it. c.w. Hermetic
deep. The work displays both internal complexity and a wealth of connections to external phenomena (history, culture, etc.).
detailed. Full of small features.
dog's breakfast, a. Defined by Christopher Fox as a flute concerto by R. Murray Schaefer.
economic. A close match between means and ends.
effective. Music that pushes the listener. Probably the worst thing I could say about a piece of music.
elegant. When faced with a valley that one wishes to cross, a robust solution is to fill it in, an efficient solution is to build a bridge, and an elegant solution is to fly over in a dirigible, wearing white kid gloves.
empty. On zen-ish days, a compliment. On ordinary days, not.
fine.
flat. Without detail.
gnarly. Yes, I did grow up in Southern California.
hermetic. I don't understand it, may never understand it, but I suspect that its worth trying to understand it.
inflated. When market value exceeds intrisic value.
kitchen sink. Indicates that the composer has used at least one more element than was necessary. cw laundry list
laundry list. Indicates that the composer has used up every available element or combination of elements. cw kitchen sink
loose.
loss, a. The effort expended was not worth the result. see also totaled
luxurious. The enjoyment of means well in excess of needs.
mahnkopfed. pubescent. see also complicated.
mannered.
mess, a. When intended (i.e. Christian Wolff, Burdocks) a playful, delightful thing, when not intended, neither playful nor delightful.
movie music.
19th Century.
Poland, (makes you want to invade). The effect of Beethoven on a listener cw the effect of Rossini on a listener. see Pynchon, GR pp440.
precious. Usually used as a negative, indicating the over-application of effects that are best held in reserve.
quality.
real. In a world of cheap reproductions and throw-aways, who could ask for anything more? Reserved for a very small shortlist of pieces.
smart.
strategic. Indicates the use of long-term planning. cw tactic
tactic. A move applied on a provisional or one-off basis. cw strategic
talent. As in "there's no stopping it": a sarcastic response to an underwhelming effort.
tight. Precise, without excess.
ugly. Not neccessarily a negative. I honestly believe that there is not enough good ugly music in the world; the problem is bad and indifferent music, and ugly music can be good, bad, or indifferent.
totaled. A total loss, nothing to recover.
vivid. A dangerous term. While I like music that makes certain features or details vivid, I can't handle music that is only about pushing all levels to 11. A term I have learned from Alvin Lucier and Tom Robbins.