I need about 7 hours, my girlfriend needs 8-10, so we tend to compromise somewhere in the middle, with me continuing to read for a while after she's fallen asleep. I must not sleep much longer than 8 hours though, or I end up lethargic and unproductive and also unable to fall asleep the next night.

For me, the main sleep-related productivity boosters are making sure I can and do actually sleep, which took me years, (lying awake until 4am+ sucks big time) and making sure I'm ready to work at about 8-8:30 in the morning. 8:30 to 11:30 easily is my most productive time of day, probably 2-3 times as productive as other times.

I wouldn't bother trying to reduce sleep time. Optimise your awake time for happiness and productivity.