Nepenthes definitely exhibit hybrid vigor. It seems the strongest, easiest growers are hybrids between a lowland x highland. N. Mixta is the perfect example: maxima x northiana. Its been around for more than 100 years and grows vigorously in both lowland and highland conditions.
I would like to see more breeding along lines that emphasize certain shapes and colors, say echinostoma x ramispina, or rafflesiana x burbidgea.