After years of reading hexameters, I can now usually read unseen verses in the correct meter without stumbling. I have had a much harder time with iambic trimeters, however, even after reading the entire Cyclops. All those substitutions! and the ancipites! This morning on the bus, while reading the opening to Medea, it finally clicked.
Using Euripides as my first serious exposure to trimeters was probably not the smartest decision.