DC's STA engine called "design-time", it's not good from long time ago.
Synopsys wishes to replace design-time with the engine of PT, they used to announce the 2003.06 release will using PT's engine, but seems not.... It's not fair for customer to pay a lot of money to buy DC with a cropping timing engine.
Some ic design company start adopting the STA tool from Incentia, it's performance is much better than PT. My company also buys the logic synthesis from Incentia, the timing results from synthesis tool is 100% consistent with STA.