Can a MacBookPro6,1 drive a Dell U2713HM via DisplayPort?
The answer is yes - using the Monoprice 3ft DisplayPort to Mini DisplayPort cable it works perfectly.

Before the cable arrived I used DVI, through the Apple Mini DisplayPort to Dual-Link DVI Adapter - adapters with firmware version 1.03 work reliably though 1.02 did not. Apple replaced mine because of this, see support bulletin here. It's nice to put the bulky adapter and bulky DVI cable away.