I go for a happy medium between 5,000 and 10,000. I have always changed my oil at 7,500. Always used synthetic too. I do a mix of city/highway driving which is my reasoning for the 7,500. I'm just about to hit 36,000 miles now.

'00 Insight "Wazabi" -75,000+ miles
'03 Toyota Matrix - 81,000+ miles
'03 HCH-CVT-OSBM-41,000+ miles (retired 04-10-06)
"I'm very secure with my little Insight, no Prius envy here."