I'd say about 90% of the pills I've had have been good luckily. The ones that havent worked -

Took 2 'CU's in Australia when I was on holiday, got charged about 5 times the price I pay here and nothing happened at all BUMPED!

Took 2 blue dolphins on NYE 04, was throwing up real bad all night

Took 6 mitzibishies one night in a club which turned out to be ketamine, that was a nasty experience......