I guess I'm lucky because I never really had a bad acid trip.
Coolest acid experiences: Playing in the coral reefs in Okinawa at sunset, hiking in Yosemite, and many a Dead show back in the day. Oh yeah, and one time I went to a Rosicrusian Eqyptian Museum with mummies and stuff while tripping, and that was pretty intense.
In all, I've probably done acid about 20 times (more than half of those times was during a 6-month stay in Okinawa, Japan. Not sure why I stopped other than the novelty had worn off, and I have a general aversion to chemicals (due to inconsistencies and lack of health/safety standards). Also, tripping can be a long time commitment, and I generally don't like tripping for more than a few hours at a time.
I've always found magic mushrooms more enjoyable as a high, and generally not as long lasting, although it is definitely an acquired taste (makes me shiver just thinking about eating those nasty tasting things).
Although I still enjoy cannabis on a regular basis, I rarely do hallucinogens anymore.
Sometimes the moon howls, and the wolf is silent...
ADG